Catalyst for dehydrogenation reaction, and method for producing olefin

Abstract

This catalyst for a dehydrogenation reaction comprises: a main phase constituted from a perovskite type composite oxide represented by the general formula (A1-xA'x)(Zr1-y-zByB'z)O3-δ (here, A is at least one element selected from among alkaline earth metals, A' is at least one element among La and Y, B is at least one element among Ti and Ce, B' is at least one element selected from among Y, Sc, Yb, Al, In and Nd, 0≤x≤0.4, 0≤y, 0.1≤z≤0.7, 0<(1-y-z), and δ denotes the oxygen deficiency amount); and a subsidiary phase constituted from at least one of two types of carbonate represented by the general formulae ACO3 and A'CO3 (here, A and A' are the same as A and A' that constitute the perovskite type composite oxide).

Description

Dehydrogenation catalyst and method for producing olefins

[0001] The present disclosure relates to a catalyst for a dehydrogenation reaction and a method for producing olefins.

[0002] Conventionally, various catalysts have been proposed as catalysts for dehydrogenation reactions, such as methane oxidative coupling catalysts for producing ethylene and the like from methane. For example, Patent Document 1 discloses a catalyst having the general formula Li ２ ABO ４ (A is one or more selected from the group consisting of Ca, Sr, Ba, and Mg, and B is Si and / or Ge), it has been shown that hydrocarbons having two or more carbon atoms can be produced from methane with high yield and high selectivity.

[0003] Patent No. 7116479

[0004] However, the above-mentioned methane oxidative coupling catalysts and the like are generally used under relatively high temperature conditions of around 800°C, which has led to the problem of the catalyst being prone to degradation. Furthermore, if the energy required to proceed with the reaction is large to proceed under relatively high temperature conditions, it becomes difficult to reduce the cost required for the reaction, which has hindered industrialization. Therefore, a catalyst that can exhibit higher catalytic activity even under relatively low temperature conditions has been desired. For example, the above-mentioned Patent Document 1 discloses that, among Li-containing composite oxide catalysts satisfying the general formula, catalysts having a specific composition exhibit relatively high activity even under a lower temperature condition of 750°C. However, sufficient research has not been conducted on techniques for improving catalytic activity under lower temperature conditions. Furthermore, just as the above-mentioned catalysts with specific compositions were able to ensure activity under relatively low temperature conditions, optimizing the catalyst composition can provide a catalyst that exhibits high activity even under lower temperature conditions. However, it may be difficult to newly discover catalysts with such specific compositions and therefore difficult to adopt. Therefore, a technique that enables improved catalytic activity at low temperatures using a simpler method has been desired. The methane oxidative coupling reaction is a type of dehydrogenation reaction. However, not only the methane oxidative coupling reaction but also all dehydrogenation reactions generally proceed under similar high-temperature conditions. Therefore, improving catalytic activity under such low-temperature conditions has been a common challenge for dehydrogenation catalysts.

[0005] The present disclosure can be realized in the following aspects. (1) According to one aspect of the present disclosure, a dehydrogenation catalyst is provided. The dehydrogenation catalyst agent 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 lanthanum (La) and yttrium (Y), B is at least one element of 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 0≦x≦0.4, 0≦y, 0.1≦z≦0.7, and 0<(1−y−z), and δ represents the amount of oxygen vacancy), and a main phase composed of a perovskite-type composite oxide represented by the general formula ACO ３ and A'CO ３(where A and A' are elements common to A and A' constituting the perovskite complex oxide). With this form of dehydrogenation catalyst, the catalytic activity under relatively low temperature conditions can be improved by the simple method of providing a main phase composed of the perovskite complex oxide and a subphase composed of the carbonate. (2) In the dehydrogenation catalyst of the above form, A may contain at least barium (Ba). With this configuration, the main phase, which mainly realizes the activity of promoting the dehydrogenation reaction, can be formed from a perovskite oxide containing barium (Ba), an alkaline earth metal element with a particularly low electronegativity, thereby further improving the catalytic activity of the dehydrogenation catalyst. (3) In the dehydrogenation catalyst of the above embodiment, when a powder X-ray diffraction pattern using CuKα radiation indicates that the peak with the greatest intensity among peaks corresponding to the perovskite-type composite oxide constituting the main phase is a first peak, and that the peak with the greatest intensity among peaks corresponding to the carbonate constituting the subphase is a second peak, the ratio of the intensity of the second peak to the intensity of the first peak may be 0.2 or less. This configuration makes it possible to enhance catalytic activity under relatively low temperature conditions while ensuring sufficient activity as a dehydrogenation catalyst. (4) In the dehydrogenation catalyst of the above embodiment, the first peak may exist in a diffraction angle 2θ range of 28.0-32.0°, and the second peak may exist in a diffraction angle 2θ range of 23.0-25.0°, and the ratio of the intensity of the second peak to the intensity of the first peak may be 0.0711 or less. This configuration further enhances the effect of improving catalytic activity under relatively low temperature conditions. (5) In the dehydrogenation catalyst of the above embodiment, the subphase is substantially barium carbonate (BaCO ３ ) alone. With such a configuration, the activity of the dehydrogenation catalyst can be further enhanced. (6) In the dehydrogenation catalyst of the above embodiment, the perovskite-type composite oxide may be composed of BaZr １－ｚ B'ｚ O ３－δ (wherein B' may be at least one element selected from the group consisting of yttrium (Y) and scandium (Sc)). Such a configuration can further enhance the activity for promoting the dehydrogenation reaction. (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. Such a configuration can improve the catalytic activity for promoting the methane oxidative coupling reaction even under relatively low temperature conditions. (8) According to another embodiment of the present disclosure, there is provided a method for producing olefins. This olefin production method produces olefins containing ethylene from a feed gas containing methane using the methane oxidative coupling catalyst described in (7). According to this embodiment of the olefin production method, olefins containing ethylene can be produced using the methane oxidative coupling catalyst even under relatively low temperature conditions. The present disclosure can be realized in various forms other than those described above, for example, a method for producing a dehydrogenation catalyst, an apparatus including a dehydrogenation catalyst, or an olefin production apparatus including a methane oxidative coupling catalyst.

[0006] 1 is an explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst; 2 is an explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst; 3 is an explanatory diagram showing various dehydrogenation reactions that can be promoted by a dehydrogenation catalyst; 4 is an explanatory diagram showing the results of an investigation into the performance of a dehydrogenation catalyst; 5 is an explanatory diagram showing XRD charts of samples S1 to S3, and S5 side by side; 6 is an explanatory diagram showing enlarged XRD charts of samples S1 to S3, and S5; 7 is an explanatory diagram showing XRD charts of samples S4 and S6 side by side; 8 is an explanatory diagram showing enlarged XRD charts of samples S4 and S6; 9 is an explanatory diagram showing an XRD chart of sample S3; 10 is an explanatory diagram showing XRD charts of samples S7 to S9 side by side; 11 is an explanatory diagram showing enlarged XRD charts of samples S7 to S9; and 12 is an explanatory diagram showing an XRD chart of sample S9.

[0007] A. Dehydrogenation catalyst: The dehydrogenation catalyst of this embodiment is a composite oxide having a main phase composed of a perovskite-type composite oxide represented by the following general formula (1), and a subphase composed of at least one of two carbonates represented by the following general formulas (2a) and (2b).

[0008] (A １－ｘ A' ｘ ) (Zr １－ｙ－ｚ B ｙ B' ｚ ) O ３－δ … (1) ACO ３ … (2a) A'CO ３ … (2b)

[0009] Here, 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 of the following formulas (3a) to (3d). δ represents the amount of oxygen deficiency required to achieve electrical neutrality, and is, for example, 0≦δ≦0.5.

[0010] 0≦x≦0.4 … (3a) 0≦y … (3b) 0.1≦z≦0.7 … (3c) 0<(1-y-z) … (3d)

[0011] In the formulas (2a) and (2b), A and A' are elements common to A and A' constituting the perovskite complex oxide represented by formula (1).

[0012] In the dehydrogenation catalyst of this embodiment, the perovskite-type composite oxide of formula (1) constituting the main phase has activity as a dehydrogenation catalyst. 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.

[0013] 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, specifically olefins including ethylene, from methane. Also included are various reactions for producing hydrogen from various hydrocarbon compounds, including hydrocarbons and alcohols, by dehydrogenation. 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.

[0014] 1 and 2 are explanatory diagrams showing an example of a reaction including a dehydrogenation reaction, in which the dehydrogenation catalyst of the present embodiment is a methane oxidative coupling catalyst and the methane oxidative coupling reaction proceeds on the catalyst. The function of the dehydrogenation catalyst of the present embodiment shown in FIGS. 1 and 2 will be described in detail later.

[0015] B. Perovskite-type composite oxide constituting the main phase: As described above, in the dehydrogenation catalyst of this embodiment, at least the perovskite-type composite oxide of formula (1) constituting the main phase has activity as a dehydrogenation catalyst. The perovskite-type composite oxide of formula (1) will be further described below.

[0016] The perovskite complex oxide of formula (1) is ABO ３The perovskite structure has a so-called A site, which contains at least one element selected from alkaline earth metals. 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." It is more preferable that element A contains at least barium (Ba).

[0017] The perovskite complex oxide of formula (1) may further contain at least one element selected from lanthanum (La) and yttrium (Y) at the A site of the perovskite structure. However, lanthanum (La) and yttrium (Y) are not essential. Hereinafter, the lanthanum (La) and yttrium (Y) contained at 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 the above-mentioned formula (1) satisfy formula (3a).

[0018] The perovskite complex oxide of formula (1) also contains zirconium (Zr) in the so-called B site of the perovskite structure. This perovskite complex oxide may further contain at least one element selected from titanium (Ti) and cerium (Ce) in the B site. However, titanium (Ti) and cerium (Ce) are not essential. Hereinafter, the titanium (Ti) and cerium (Ce) contained in the B site will also be referred to as "element B." The perovskite complex 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) in 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 composite oxide of formula (1), the contents of Zr, element B, and element B' satisfy formulas (3b) to (3d) in the above-mentioned formula (1).

[0019] In the perovskite complex oxide of formula (1), it is desirable that x satisfy the following formula (3e), which can further enhance the activity for promoting the dehydrogenation reaction.

[0020] 0≦x≦0.2… (3e)

[0021] Furthermore, the perovskite complex oxide of formula (1) preferably has a perovskite structure represented by the following general formula (4), which can further enhance the activity of promoting the dehydrogenation reaction.

[0022] BaZr １－ｚ B' ｚ O ３－δ... (4) where B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), indium (In), and neodymium (Nd).

[0023] In this case, B' is yttrium (Y), that is, the perovskite complex oxide of formula (4) is BaZr １－ｚ Y ｚ O ３－δ and B' is scandium (Sc), that is, the perovskite complex oxide of formula (4) is BaZr １－ｚ Sc ｚ O ３－δ It is particularly desirable that z be in the range of 0.1≦z≦0.5 when B′ is yttrium (Y). This makes it possible to further enhance the activity of promoting the dehydrogenation reaction.

[0024] The perovskite complex oxide of formula (1) has proton conductivity and at least one of electron conductivity and hole conductivity in addition to the activity of promoting the dehydrogenation reaction. The perovskite complex oxide represented by formula (1) constituting the main phase of the dehydrogenation catalyst of this embodiment has activity as a dehydrogenation catalyst and at least one of proton conductivity, electron conductivity and hole conductivity, as disclosed by the present inventors in WO 2022 / 270403.

[0025] C. Carbonates Constituting the Subphase: As described above, the dehydrogenation catalyst of this embodiment has a subphase composed of at least one of the two carbonates represented by formulas (2a) and (2b). As a result of having such a structure, the catalytic activity is improved even under relatively low temperature conditions. Specifically, even when the dehydrogenation catalyst is used under relatively low temperature conditions, for example, at about 650-700°C, high activity that promotes the dehydrogenation reaction can be achieved. The subphase is preferably composed of either one of the two carbonates represented by formulas (2a) and (2b). Furthermore, the subphase is preferably composed of at least the carbonate represented by formula (2a).

[0026] Furthermore, in this embodiment, the phrase "two types of carbonates represented by formulas (2a) and (2b)" constituting the subphase does not mean that the carbonate represented by formula (2a) or the carbonate represented by formula (2b) is composed of a single type of carbonate, but rather includes the case where at least one of the carbonate represented by formula (2a) and the carbonate represented by formula (2b) is composed of multiple types of carbonates. That is, the subphase may contain multiple types of carbonates of A or multiple types of carbonates of A' (where A is at least one element selected from alkaline earth metals, A' is at least one element of lanthanum (La) and yttrium (Y), and A and A' are elements common to A and A' constituting the perovskite-type composite oxide of formula (1) constituting the main phase).

[0027] The subphase may contain components other than the carbonates represented by formulas (2a) and (2b). For example, when the dehydrogenation catalyst of this embodiment is produced by a solid-phase method as described below, a trace amount of a compound other than the perovskite-type oxide may be synthesized in the process of synthesizing the perovskite-type composite oxide of formula (1) that constitutes the main phase, and as a result, the synthesized compound may be contained in the subphase together with the carbonates represented by formulas (2a) and (2b).

[0028] In a powder X-ray diffraction pattern using CuKα radiation, when the peak with the greatest intensity among peaks corresponding to the perovskite-type composite oxide constituting the main phase of the dehydrogenation catalyst of this embodiment is defined as the first peak, and the peak with the greatest intensity among peaks corresponding to the carbonate 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 0.2 or less. The dehydrogenation catalyst of this embodiment can improve its catalytic activity under relatively low temperature conditions by including the carbonate-containing subphase, as described below. However, in the dehydrogenation catalyst of this embodiment, its activity as a dehydrogenation catalyst is mainly achieved by the main phase. By setting the ratio of the intensity of the second peak to the intensity of the first peak to 0.2 or less, it is possible to improve the catalytic activity under relatively low temperature conditions while sufficiently ensuring the activity as a dehydrogenation catalyst. In the dehydrogenation catalyst of this embodiment, from the viewpoint of ensuring the effect of improving catalytic activity under relatively low temperature conditions, the ratio of the intensity of the second peak to the intensity of the first peak is preferably 0.005 or more, and more preferably 0.01 or more.

[0029] In the dehydrogenation catalyst of this embodiment, for example, the first peak may exist in the range of diffraction angle 2θ=28.0-32.0°, the second peak may exist in the range of diffraction angle 2θ=23.0-25.0°, and the ratio of the intensity of the second peak to the intensity of the first peak may be 0.0711 or less. With such a configuration, the effect of improving catalytic activity under relatively low temperature conditions can be further enhanced. Specifically, when the first peak exists in the range of diffraction angle 2θ=28.0-32.0° and the second peak exists in the range of diffraction angle 2θ=23.0-25.0°, the perovskite-type composite oxide constituting the main phase is BaZr １－ｚ Y ｚ O ３－δ and the carbonate constituting the subphase is barium carbonate (BaCO ３ ) or when the perovskite complex oxide constituting the main phase is BaZr １－ｚ Sc ｚ O ３－δand the carbonate constituting the subphase is barium carbonate (BaCO ３ ) can be used.

[0030] The powder X-ray diffraction pattern using CuKα radiation for the dehydrogenation catalyst of this embodiment may include peaks corresponding to compounds other than the perovskite complex oxide constituting the main phase and the carbonate constituting the subphase. For example, as described above, when a compound other than the perovskite complex oxide of formula (1) and other than the carbonate represented by formula (2a) or (2b) (e.g., an oxide other than the perovskite complex oxide of formula (1)) is generated as a by-product in the process of synthesizing the dehydrogenation catalyst of this embodiment, the pattern may include peaks corresponding to such a by-product. Specifically, for example, when the perovskite complex oxide constituting the main phase is BaZr １－ｚ Sc ｚ O ３－δ and the carbonate constituting the subphase is barium carbonate (BaCO ３ ), then Ba ３ Sc ４ O ９ The peak may include a peak corresponding to

[0031] The dehydrogenation catalyst of this embodiment configured as described above has a main phase composed of the perovskite-type composite oxide represented by the above-described formula (1) and a subphase composed of at least one of the two carbonates represented by the above-described formulas (2a) and (2b), thereby enabling improved catalytic activity even under relatively low temperature conditions. In the dehydrogenation catalyst of this embodiment, the activity to promote the dehydrogenation reaction is achieved mainly by the perovskite-type composite oxide constituting the main phase, as described above. In such a dehydrogenation catalyst, the further inclusion of a subphase containing at least one of the two carbonates represented by the formulas (2a) and (2b) enables improved catalytic activity even under relatively low temperature conditions.

[0032] As described above, Figures 1 and 2 show 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. In the methane oxidative coupling reaction, a reaction that produces methyl radicals from methane, as shown in the following formula (5), proceeds, and further, reactions of the following formulas (6) and (7) (see Figure 1) and reactions of the following formulas (8) and (9) (see Figure 2) proceed, resulting in the production of C radicals such as ethylene. ２ The overall reaction for producing ethylene by the oxidative coupling of methane is represented by the following formula (10):

[0033] CH ４ → ・CH ３ +H ＋ +e － … (5) 2 CH ３ +1 / 2O ２ → C ２ H ４ +H ２ O... (6) 1 / 2O ２ +2H ＋ +2e － → H ２ O … (7) 2・CH ３ → C ２ H ６ → C ２ H ４ +2H ＋ +2e － … (8) O ２ +4H ＋ +4e － → 2H ２ O ... (9) 2CH ４ +O ２ → C ２ H ４ +2H ２ O... (10)

[0034] In dehydrogenation reactions such as methane oxidative coupling reactions, electron transfer appropriate for the catalytic reaction is desirable. For example, in methane oxidative coupling reactions, electrons are transferred between the catalyst and methane. The ease of electron transfer is thought to depend on the base sites of the catalyst, and the base sites are thought to be affected by the electronegativity of the elements contained in the catalyst. That is, catalysts (e.g., basic oxide catalysts) containing metal elements with low electronegativity (basic metal elements) are thought to have an increased number of base sites, resulting in improved catalytic performance. The dehydrogenation catalyst of this embodiment ensures high activity as a dehydrogenation catalyst by forming the main phase, which primarily realizes the activity of promoting the dehydrogenation reaction, from a perovskite-type oxide containing an alkaline earth metal element with low electronegativity, as shown in formula (1). In particular, it is preferable to use a perovskite-type oxide containing barium (Ba), which has low electronegativity, as the alkaline earth metal.

[0035] A known problem with such dehydrogenation catalysts is that carbon dioxide is produced as a by-product during the reaction. For example, in the methane oxidative coupling reaction shown in the above-described formulas (5) to (10), a side reaction, a methane peroxidation reaction, i.e., a complete oxidation reaction in which carbon dioxide and water are produced from methane, can proceed. The progression of such a reaction suppresses the dehydrogenation reaction that should proceed, such as the methane oxidative coupling reaction. The dehydrogenation catalyst of this embodiment has a subphase containing the carbonate represented by the above-described formula (2a) or formula (2b). Therefore, when the catalyst comes into contact with methane, which is a reducing gas, in a reducing atmosphere during the reaction, one oxygen atom (O) is removed from the carbonate on the outermost surface of the catalyst, thereby producing carbon dioxide (CO ２) is considered to result in a structure similar to that in the case of carbon dioxide adsorption on the catalyst surface. As a result, a reaction field similar to that in which carbon dioxide generation due to the complete oxidation reaction is locally suppressed is formed, which is considered to result in improved selectivity for the desired reaction to proceed and enhanced catalytic activity. As such, in the dehydrogenation catalyst of this embodiment, the catalytic activity is considered to be improved by the interaction between the perovskite-type oxide in the main phase, which primarily exhibits catalytic activity, and the carbonate in the subphase. Note that, in order to obtain the effect of suppressing the generation of carbon dioxide as a by-product as described above, it is sufficient for the dehydrogenation catalyst to contain a carbonate in the subphase. Therefore, it is considered that the same effect can be obtained whether the cation constituting the carbonate is an alkali metal or an alkaline earth metal. Therefore, the dehydrogenation catalyst of the present specification only needs to have a subphase composed of at least one of the two carbonates represented by formulas (2a) and (2b).

[0036] In this case, it is more desirable that the carbonate constituting the subphase contains a carbonate of an alkaline earth metal having a lower electronegativity, that is, that the subphase contains at least a carbonate represented by formula (2a). This can further enhance the activity of the dehydrogenation catalyst. Among these, barium carbonate (BaCO), which has a particularly low electronegativity, is preferred as the carbonate of formula (2a). ３ It is preferable to use a carbonate containing an alkaline earth metal that serves as a basic site, and it is more preferable that the subphase be composed essentially of barium carbonate. In this way, by introducing a carbonate containing an alkaline earth metal that serves as a basic site, the concentration of the alkaline earth metal in the vicinity of the reaction field can be increased, thereby securing more basic sites in the dehydrogenation catalyst and, for example, making it possible to increase catalytic activity even under lower temperature conditions.

[0037] Furthermore, by providing a subphase containing a carbonate represented by formula (2a), which is a carbonate of an alkaline earth metal, it is possible to further increase the content of the alkaline earth metal in the dehydrogenation catalyst. For example, Ba(Zr,Y)O is used as a perovskite-type oxide represented by formula (1). ３ Using the oxides of the series, barium carbonate (BaCO) was used as the carbonate of formula (2a). ３The following will explain the case where Ba(Zr,Y)O is used as an example. ３ The barium (Ba) content per 0.1 g of the system oxide is calculated to be 0.00036 to 0.00037 mol. On the other hand, barium carbonate (BaCO ３ The Ba content per 0.1 g of Ba(Zr,Y)O is 0.00051 mol. ３ When comparing the Ba(Zr,Y)O oxide with barium carbonate, the Ba content per 0.1 g is higher in barium carbonate. ３ By mixing a small amount of alkaline earth metal carbonate such as barium carbonate with the main phase of a base oxide or the like, it is possible to obtain a catalyst that is rich in alkaline earth metal (easy to secure basic sites) while maintaining catalytic performance, thereby improving catalytic performance.

[0038] Furthermore, in the dehydrogenation catalyst of this embodiment, catalytic activity can be improved by the simple method of mixing a perovskite-type oxide that realizes catalytic activity with a carbonate represented by formula (2a) or (2b). That is, without using a catalyst with a particularly complex composition or optimizing a new material composition, the perovskite-type oxide known as a dehydrogenation catalyst can be used to enhance the activity of promoting dehydrogenation even under relatively low temperature conditions, for example, around 650-700°C.

[0039] D. Other Dehydrogenation Reactions: FIG. 3 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. 3 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 oxidative coupling reactions of methanes, is also referred to as "oxidative coupling catalysts of methanes." Note that in formulas (13) to (22) in FIG. 3, 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. 3 has one or two hydrogen atoms in the methane molecule substituted with the above-mentioned substituents. When a single 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), a phenyl group (—C ６ H ５ ) etc.

[0040] In FIG. 3 , formula (11), like formula (10), represents the reaction of producing ethylene from methane. When the dehydrogenation catalyst of this embodiment functions as a methane oxidative coupling catalyst, it not only promotes the reaction of producing ethylene, which has two carbon atoms, from methane as shown in formula (11), but also promotes the reaction of producing hydrocarbons having two or more carbon atoms. That is, by using the dehydrogenation catalyst of this embodiment as a methane oxidative coupling catalyst, olefins including ethylene can be produced from a feed gas containing methane. Formula (12) represents the reaction of producing polyethylene by further progressing the polymerization reaction via the methane oxidative coupling reaction. Unlike formula (10), formulas (11) to (22) only show the changes in methane and methane derivatives among the molecules involved in the reaction.

[0041] Equations (11) and (12) show reactions using methane as a reactant. Equations (13) and (14) show reactions using BACH ２ Formulas (15) and (16) show the reaction in which a methane derivative represented by the formula (15) is used as a reactant. ３ Formulas (17) and (18) show the reaction in which a methane derivative represented by the formula (17) is used as a reactant. ３ The formulas (19) and (20) show the reaction of a methane derivative represented by the formula (19) and methane as a reactant. ３ and methane derivatives represented by the formula: ２ H ２ Formulas (21) and (22) show the reaction in which a methane derivative represented by the formula CABH ２ The reaction using methane derivatives represented by the formula (I) and methane as reactants is shown below.

[0042] Formulas (11), (13), (15), (17), (19), and (21) represent hydrocarbons with one carbon atom (methane) and methane derivatives (hereinafter referred to as "C １ a hydrocarbon having two carbon atoms (ethylene) or an ethylene derivative (hereinafter referred to as "C ２ The formulas (12), (14), (16), (18), (20), and (22) show the reactions that produce C １ The reaction to produce a polymer is shown using a reactant selected from hydrocarbons. １ Hydrocarbons C ２ After the hydrocarbons are produced, these C ２ The hydrocarbons may be further polymerized with each other, and C may be attached to the end of the molecule. １ The hydrocarbons may be polymerized sequentially to form a polymer, or both of these reactions may proceed.

[0043] To explain the reaction shown in Figure 3 more specifically, for example, if the substituents A and B in formula (14) 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 hydroxy group (-OH), polyvinyl alcohol (PVOH) is obtained as the product. If the substituent A is a phenyl group (-C ６ H ５ ), 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, and if the substituents A and B are both chlorine atoms (Cl), polyvinylidene chloride (PVDC) is obtained as the product. In formula (22), if the substituent A is a methyl group (-CH ３ ) and the substituent B is a methoxycarbonyl group (—COOCH ３ ), the product is polymethyl methacrylate (PMMA).

[0044] Although FIG. 3 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 the alkanes that 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 derivatives used in the oxidative coupling reaction of alkanes are those in which hydrogen atoms contained in the alkane molecules have been substituted with the substituents described above, but which have a covalent bond between the carbon atom to be dehydrogenated and the hydrogen atom.

[0045] The dehydrogenation catalyst of this embodiment can also be used to promote dehydrogenation reactions other than the oxidative coupling reaction of alkanes. Other dehydrogenation reactions promoted by the dehydrogenation catalyst of this embodiment include, for example, the dehydrogenation reaction of alkanes as exemplified by formula (23) in FIG. 3 , 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 an atom or atomic group as a substituent replacing hydrogen, as in formulas (13) to (22). 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. Thus, even when the dehydrogenation catalyst of this embodiment is used as a catalyst for promoting various dehydrogenation reactions, by providing a subphase containing a carbonate, it is possible to suppress the progress of a peroxidation reaction of the reactants, i.e., a side reaction in which the reactants are completely oxidized to generate carbon dioxide, and thereby obtain the effect of increasing the activity for promoting the desired dehydrogenation reaction even under relatively low temperature conditions.

[0046] E. Method for Producing Dehydrogenation Catalyst: The dehydrogenation catalyst of this embodiment can be produced, for example, by a solid-state reaction method. Specifically, raw material powders of the perovskite oxide represented by formula (1) that constitute the main phase 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. The raw material powders may be carbonates or oxides of elements A, A', B, B', and zirconium that constitute the perovskite oxide represented by formula (1). However, for at least one of element A and element A', carbonates may be used as the raw material powder. This allows the carbonates that remain in the calcination step of the solid-state reaction method without contributing to the formation of the perovskite oxide to form a subphase containing the carbonate represented by formula (2a) or (2b).

[0047] The conditions for leaving carbonate as a subphase by the solid-state reaction method are determined by the production conditions, specifically, the calcination temperature, calcination time, and raw material powder ratio, depending on the degree of element substitution at the A site and B site represented by x, y, and z in formula (1) and the corresponding combination of material powders. For example, the larger the values ​​of y and z in formula (1) and the greater the element substitution at the B site of the perovskite-type composite oxide, the more likely it is that an alkaline earth metal carbonate, such as barium carbonate, will remain as a subphase. Furthermore, the relatively lower the calcination temperature during catalyst production, the more likely it is that the carbonate will remain as a subphase. Furthermore, by increasing the amount of carbonate desired to remain as a subphase relative to the stoichiometric ratio of each raw material powder derived from formula (1) in the ratio of raw material powders mixed during dehydrogenation catalyst production, it becomes easier to form a subphase composed of the desired carbonate.

[0048] For example, Ba(Zr,Y)O ３ The main phase is composed of oxides of the system, and barium carbonate (BaCO ３ ), and the perovskite complex oxide constituting the main phase is Ba(Zr ０．８ Y ０．２ ) O ３ In this case, it is desirable that the firing temperature is about 1000-1300°C and the firing time is 5 hours or less. ０．６ Y ０．４ ) O ３ In this case, it is desirable that the firing temperature is about 1000-1300°C and the firing time is 10 hours or less. ０．６ Y ０．４ ) O ３ is Ba(Zr ０．８ Y ０．２ ) O ３ This is because the value of z in formula (1) is larger than that in the case of the perovskite-type oxide of the main phase and the carbonate of the subphase, resulting in a larger amount of element substitution at the B site, and therefore requiring a longer reaction time. In this way, the desirable production conditions can be appropriately set depending on the composition of the perovskite-type oxide that constitutes the main phase and the carbonate that constitutes the subphase.

[0049] The dehydrogenation catalyst of this embodiment may be prepared by a method other than the solid-state reaction method described above. Specifically, the perovskite-type composite oxide constituting the main phase and the carbonate constituting the subphase may be prepared separately and then mixed. The amount of the subphase in the resulting dehydrogenation catalyst can be adjusted by adjusting the mixing ratio. For example, it is desirable to set the mixing ratio so that when a powder X-ray diffraction pattern using CuKα radiation is obtained for the prepared dehydrogenation catalyst, the ratio of the intensity of the second peak to the intensity of the first peak described above is 0.2 or less. Even when preparing a dehydrogenation catalyst in this manner, the previously described effects of providing a subphase containing a carbonate represented by formula (2a) or (2b) can be obtained. Furthermore, the dehydrogenation catalyst of this embodiment may be prepared by synthesizing a perovskite oxide that has catalytic activity and will constitute the main phase, and then contacting this perovskite oxide with a gas containing carbon dioxide (e.g., high-purity carbon dioxide or air) to generate, within the perovskite oxide, a carbonate of the alkaline earth metal contained in the perovskite oxide (e.g., barium carbonate).

[0050] 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.

[0051] FIG. 4 is an explanatory diagram showing the results of examining the performance of six types of dehydrogenation catalysts, samples S1 to S6. Of samples S1 to S6, samples S1 to S4 are samples in which the perovskite-type composite oxide constituting the main phase was synthesized by a solid-state reaction method, and a subphase composed of carbonate was observed in the resulting dehydrogenation catalyst. Samples S5 and S6 are comparative samples in which the perovskite-type composite oxide was synthesized by a complex polymerization method, and a subphase composed of carbonate was not observed in the resulting dehydrogenation catalyst. In the following explanation and in the figures, the number of oxygen atoms in the formula is represented by "O ３ ", but these descriptions are "O ３－δ " and does not mean that δ is strictly 0.

[0052] <Preparation of each sample> [Samples S1 to S3] Catalysts of samples S1 to S3 (main phase: BaZr ０．８ Y ０．２ O ３ ) were prepared by a solid-state reaction method. 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.) were used as raw material powders. These raw material powders were weighed so that the ratio of metal elements was the target composition ratio. 5 mm diameter balls and ethanol were then 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 sieve with a mesh size of 250 μm. The obtained powders were then fired for 5 hours at temperatures (heat treatment temperatures) of 1200°C for sample S1, 1300°C for sample S2, and 1100°C for sample S3. 5 mm diameter balls and ethanol were added to the obtained powders, which were then ball milled again and mixed for 15 hours. Thereafter, the ethanol component was removed to obtain a solid component, which was then sieved using a sieve with 250 μm openings to obtain dehydrogenation catalysts as samples S1 to S3.

[0053] [Sample S4] The target composition of the main phase is BaZr ０．６ Y ０．４ O ３A dehydrogenation catalyst as sample S4 was prepared in the same manner as sample S2, except that:

[0054] [Samples S5 and S6] Catalyst of sample S5 (composition formula: BaZr ０．８ Y ０．２ O ３ ) and the catalyst of sample S6 (composition formula: BaZr ０．６ Y ０．４ O ３ ) was prepared by a complex polymerization method. 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) were used as raw material powders. These raw material powders were weighed so that the ratio of metal elements was the composition ratio of the above-mentioned composition formula. Then, a citric acid aqueous solution and propylene glycol were added to the raw material powders 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. The solution was then slowly heated to 300°C to obtain a polymer in which each metal element was dispersed. The obtained polymer was then heat-treated at 400°C for 2 hours to carbonize it, and the carbonized polymer was then pulverized in an agate mortar to obtain a catalyst powder precursor. The obtained catalyst powder precursor was heat-treated for 6 hours at a temperature (heat treatment temperature) of 1200°C for sample S5 and 1300°C for sample S6, thereby obtaining powdered dehydrogenation catalysts as samples S5 and S6.

[0055] [Samples S7 to S9] Catalysts of samples S7 to S9 (main phase: BaZr ０．４ Sc ０．６ O ３) were prepared by a solid-state reaction method. Barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and scandium oxide (manufactured by Hunan Oriental Scandium Co., Ltd.) were used as raw material powders. For samples S7 and S8, the raw material powders were weighed so that the ratio of metal elements was the target composition ratio. For sample S9, only the barium carbonate raw material powder was weighed so that the ratio of metal elements was 1.2 times the target composition ratio, and the other raw material powders were weighed so that the ratio of metal elements was the target composition ratio. Samples S7 and S9 were weighed so that the total weight of the raw material powder was 80 g, and sample S8 was weighed so that the total weight of the raw material powder was 650 g. 5 mm diameter balls and ethanol were then added and mixed using a ball mill for 15 hours. The ethanol component was then removed to obtain the solid component, which was then sieved using a sieve with a mesh size of 250 μm. The resulting powder was calcined at a temperature of 1300°C (heat treatment temperature) for 5 hours. 5 mm diameter balls and ethanol were added to the resulting powder, which was then ball milled again and mixed for 15 hours. The ethanol component was then removed to obtain a solid component, which was then sieved using a sieve with 250 μm openings to obtain dehydrogenation catalysts as samples S7 to S9.

[0056] <Derivation of Peak Intensity Ratio> For samples S1 to S9, the peak intensity ratio (second peak intensity / first peak intensity) of the main phase to the subphase was determined by powder XRD analysis. A SmartLab-3kw (manufactured by Rigaku Corporation) was used as the X-ray diffractometer. The measurement conditions for the powder XRD method were a scanning range (2θ) of 10°-80°, a step width of 0.02°, and a scanning speed of 20° / min, and measurements were performed using a focusing optical system. CuKα radiation was used as the X-ray source under conditions of 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, and background removal was performed using the Sonnevelt-Visser method with a peak width threshold of 1.0 and an intensity threshold of 0.01. 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 complex oxide constituting the main phase, and a second peak, which is the maximum peak intensity of the carbonate constituting the subphase, were identified, and the ratio of the intensity of the second peak to the intensity of the first peak was calculated.

[0057] FIG. 5 is an explanatory diagram showing XRD charts of samples S1 to S3 and sample S5 side by side. FIG. 6 is an explanatory diagram showing enlarged portions of the XRD charts of samples S1 to S3 and sample S5 in FIG. 5. FIG. 7 is an explanatory diagram showing XRD charts of samples S4 and S6 side by side. FIG. 8 is an explanatory diagram showing enlarged portions of the XRD charts of samples S4 and S6 in FIG. 7. FIG. 9 is an explanatory diagram showing the XRD chart of sample S3.

[0058] Fig. 10 is an explanatory diagram showing XRD charts of samples S7 to S9 side by side, Fig. 11 is an explanatory diagram showing enlarged portions of the XRD charts of samples S7 to S9 in Fig. 10, and Fig. 12 is an explanatory diagram showing the XRD chart of sample S9.

[0059] In the XRD charts shown in FIGS. 5 to 12, the perovskite-type composite oxide (BaZr ０．８ Y ０．２ O ３ , BaZr ０．６ Y０．４ O ３ , or BaZr ０．４ Sc ０．６ O ３ ) is BaZrO ３ It was confirmed that the target product was obtained by comparing the value with the literature value (ICDD number: 00-001-0890). In addition, in the XRD charts shown in Figures 5 to 12, the carbonate (BaCO ３ ) is BaCO ３ It was confirmed that the target product was obtained by comparing the value with the literature value (ICDD number: 01-076-2823). When peaks not corresponding to the above-mentioned main phase and subphase are observed in the XRD chart, it is considered that by-products are produced, for example, Ba ３ Sc ４ O ９ By comparing with the literature value (ICDD number: 00-031-0161), Ba was found to be a by-product. ３ Sc ４ O ９ As shown in FIG. 9 and FIG. 12, the results of the sample S3 and the sample S9, respectively, were obtained by the solid-state reaction method. ３ Peaks derived from BaCO ３ The peaks derived from BaZrO are mixed in the catalyst. ３ The main phase of the system and BaCO ３ Furthermore, as shown in FIG. 12, in sample S9, a subphase composed of Ba, which is a compound different from the perovskite complex oxide and carbonate, is included. ３ Sc ４ O ９ In addition, a peak corresponding to Ba was also observed in samples S7 and S8. ３ Sc ４ O ９ A peak corresponding to

[0060] In the XRD chart described above, the first peak, which has the greatest intensity among the peaks corresponding to the perovskite-type composite oxide constituting the main phase, was identified as a peak in the range of 2θ = 28.0-32.0°. Furthermore, the second peak, which has the greatest intensity among the peaks corresponding to the carbonate constituting the subphase, was identified as a peak in the range of 2θ = 23.0-25.0°. Figures 6, 8, and 11 show enlarged views of the range in which the second peak can be observed. As shown in Figures 6, 8, and 11, the second peaks associated with carbonates present in smaller amounts were identified as peaks with a maximum value in the range of 2θ = 23.0-25.0° and a half-width greater than 0.2 deg. Here, the half-width is defined as the width of the peak connecting the points where the intensity is half of the peak intensity in a peak shape having a maximum value in the range of 2θ = 23.0-25.0°. 6, 8, and 11, the half-width of the second peak is indicated by a double-headed arrow. By the above method, the second peak was identified for samples S1 to S4, S8, and S9, but for samples S5 to S7, the peak with a maximum value in the range of 2θ = 23.0-25.0°, i.e., BaCO ３ Therefore, in the column "XRD peak intensity ratio" in FIG. 4, samples S5 to S7 are described as "indistinguishable from noise."

[0061] The ratio of the intensity of the second peak to the intensity of the first peak (XRD peak intensity ratio) was defined as I2max / I1max, where I1max is the maximum value of the first peak and I2max is the maximum value of the second peak. The results of calculating the XRD peak intensity ratios for samples S1 to S4, S8, and S9 are shown in Figure 4.

[0062] As described above, samples S7, S9, and S8 were produced on different production scales, with samples S7 and S9 being smaller than sample S8. Samples S7 and S8 had the same weighed ratio of raw material powder but different production scales, as described above, and it was confirmed that the degree to which carbonates constituting the subphase were produced could differ depending on the production scale. Furthermore, samples S7 and S9 had the same production scale but different weighed ratios of raw material powder, and it was confirmed that the degree to which carbonates constituting the subphase were produced could differ depending on the weighed ratio of raw material powder.

[0063] <Catalytic Activity Evaluation Test> 0.1 g of each of the samples S1 to S9 was weighed and placed in a fixed-bed flow-type reactor. In a state where the reactor was heated to 650-700°C, a mixed gas of methane, oxygen, and nitrogen was introduced at a flow rate of CH ４ :O ２ :N ２ = 3.8:1:4, 1 atmosphere, 45 cm ３ A catalytic activity test was carried out by flowing the gas at a rate of 1 / min. This catalytic activity test was carried out with each sample heated to 650-700°C. The composition of the gas introduced into the device and the gas discharged from the device were analyzed using a micro gas chromatograph (Agilent Technologies, 3000A). As a result of the composition analysis, the C shown in Figure 4 was used as a value representing the catalytic performance of each sample. ２ Yield and CO ２ The yield was obtained. ２ The yield is the ratio of the amount of carbon atoms obtained to the amount of carbon atoms contained in the raw material methane. ２ Indicates the amount of carbon atoms contained in hydrocarbons. ２ The yield is the ratio of the amount of carbon atoms in the raw methane to the amount of CO obtained. ２ It indicates the amount of carbon atoms contained in the molecule. ２ It is believed that the higher the yield, the higher the catalytic activity as a dehydrogenation catalyst. ２ The lower the yield, the more the side reaction of producing carbon dioxide from methane is thought to be suppressed, and it can be evaluated that the selectivity of the desired dehydrogenation reaction to proceed is increased. ２Yield measurements were performed on samples S1 to S3, S5, and S7 to S9, but not on samples S4 and S6.

[0064] <Evaluation Results> As shown in FIG. 4, the C was observed between dehydrogenation catalysts having the same composition of perovskite-type composite oxides constituting the main phase. ２ By comparing the yields, it is possible to determine whether the carbonate (BaCO) of the element that constitutes the A site of the perovskite complex oxide is ３ It was confirmed that catalysts having a subphase composed of BaCO 3 have improved catalytic performance, especially when used as a dehydrogenation catalyst under relatively low temperature conditions of about 650-700°C (comparison of samples S1 to S3 with sample S5, comparison of sample S4 with sample S6, and comparison of samples S8 and S9 with sample S7). ３ From the results of comparing samples S1 to S3 having a subphase composed of the above, it can be seen that there is a desirable optimum value for the content ratio of the carbonate (XRD peak intensity ratio) to improve catalytic performance.

[0065] Furthermore, as shown in FIG. 4, there are CO ２ When comparing the yields, samples S1 to S3 had a higher CO ２ The yield was low, and samples S8 and S9 had a lower CO ２ Thus, the yield is low. ３ It was confirmed that the presence of a subphase composed of SiO 2 ) suppresses the side reaction of carbon dioxide production. Furthermore, when comparing samples S1 to S3, the higher the XRD intensity ratio, the more the side reaction of carbon dioxide production is suppressed, and the more CO 2 is produced. ２ As a result, the yield was low. It was thus confirmed that the greater the amount of subphase (carbonate) contained in the dehydrogenation catalyst, the more the side reaction of carbon dioxide production was suppressed.

[0066] The present disclosure can also be realized in the following embodiments. [Application Example 1] A dehydrogenation catalyst comprising a compound represented by the general formula (A １－ｘ A' ｘ ) (Zr １－ｙ－ｚ B ｙ B' ｚ ) O ３－δ a main phase formed of a perovskite-type composite oxide represented by the general formula ACO (where 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), satisfying 0≦x≦0.4, 0≦y, 0.1≦z≦0.7, and 0<(1−y−z), and δ represents the amount of oxygen vacancy); ３ and A'CO ３(where A and A' are elements common to A and A' constituting the perovskite complex oxide), and a subphase constituted by at least one of two carbonates represented by the following formula: (where A and A' are elements common to A and A' constituting the perovskite complex oxide). [Application Example 2] The dehydrogenation catalyst according to Application Example 1, wherein A contains at least barium (Ba). [Application Example 3] The dehydrogenation catalyst according to Application Example 1 or 2, wherein, in a powder X-ray diffraction pattern using CuKα radiation, when the peak with the greatest intensity among peaks corresponding to the perovskite complex oxide constituting the main phase is defined as a first peak, and the peak with the greatest intensity among peaks corresponding to the carbonates constituting the subphase is defined as a second peak, the ratio of the intensity of the first peak to the intensity of the second peak is 0.2 or less. [Application Example 4] The dehydrogenation catalyst according to Application Example 3, wherein the first peak exists in a diffraction angle 2θ range of 28.0 to 32.0°, the second peak exists in a diffraction angle 2θ range of 23.0 to 25.0°, and the ratio of the intensity of the second peak to the intensity of the first peak is 0.0711 or less. [Application Example 5] The dehydrogenation catalyst according to any one of Application Examples 1 to 4, wherein the subphase is substantially barium carbonate (BaCO ３ A dehydrogenation catalyst according to any one of Aspects 1 to 5, wherein the perovskite-type composite oxide is composed only of BaZr １－ｚ B' ｚ O ３－δ(wherein B' is at least one element selected from the group consisting of yttrium (Y) and scandium (Sc). [Application Example 7] The dehydrogenation catalyst according to any one of Application Examples 1 to 6, wherein the dehydrogenation catalyst is a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane. [Application Example 8] A method for producing olefins, wherein olefins including ethylene are produced from a feed gas containing methane using the methane oxidative coupling catalyst according to Application Example 7.

Claims

1. A catalyst for dehydrogenation reaction, 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 selected from lanthanum (La) and yttrium (Y), B is at least one element selected 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), 0 ≦ x ≦ 0.4, 0 ≦ y, 0.1 ≦ z ≦ 0.7, 0 < (1 - y - z) is satisfied, and δ represents the amount of oxygen deficiency), a main phase composed of a perovskite-type composite oxide, and general formulas ACO ３ and A'CO ３ (wherein A and A' are elements common to A and A' constituting the perovskite-type composite oxide), a sub-phase composed of at least one of two kinds of carbonates, and a dehydrogenation reaction catalyst characterized by comprising the same.

2. The dehydrogenation reaction catalyst according to claim 1, wherein A contains at least barium (Ba). A dehydrogenation reaction catalyst characterized by this.

3. The dehydrogenation reaction catalyst according to claim 1 or 2, in the powder X-ray diffraction pattern using CuKα rays, among the peaks corresponding to the perovskite-type composite oxide constituting the main phase, the peak with the maximum intensity is defined as the first peak, and among the peaks corresponding to the carbonate constituting the sub-phase, when the peak with the maximum intensity is defined as the second peak, the ratio of the intensity of the second peak to the intensity of the first peak is 0.2 or less. A dehydrogenation reaction catalyst characterized by this.

4. The dehydrogenation reaction catalyst according to claim 3, wherein the first peak exists in the range of diffraction angle 2θ = 28.0 - 32.0°, the second peak exists in the range of diffraction angle 2θ = 23.0 - 25.0°, and the ratio of the intensity of the second peak to the intensity of the first peak is 0.0711 or less. A dehydrogenation reaction catalyst characterized by this.

5. The dehydrogenation reaction catalyst according to any one of claims 1 to 4, wherein the secondary phase is substantially composed of only barium carbonate (BaCO ３ ). The dehydrogenation reaction catalyst is characterized by this.

6. The dehydrogenation reaction catalyst according to any one of claims 1 to 5, wherein the perovskite-type composite oxide is BaZr １－ｚ B' ｚ O ３－δ (wherein B' is at least one element of yttrium (Y) and scandium (Sc)), and the dehydrogenation reaction catalyst is characterized by this.

7. The dehydrogenation reaction catalyst according to any one of claims 1 to 6, which is a methane oxidative coupling catalyst for producing hydrocarbons having 2 or more carbon atoms from methane. A dehydrogenation reaction catalyst characterized by this.

8. A method for producing an olefin, characterized by producing an olefin containing ethylene from a raw material gas containing methane using the methane oxidative coupling catalyst according to claim 7. A method for producing an olefin.

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