Ammonia synthesis catalyst

Abstract

The present invention is a composite oxide which comprises an oxide of a metal element L and an oxide of a metal element N, has a composition represented by general formula (1), and has the properties (a) to (d).　LnN1-n (1) (a) The metal element L comprises (i) a Group-1 element, (ii) a Group-2 element, or (iii) a Group-1 element and a Group-2 element; (b) the metal element N comprises a Group-1 or Group-2 element other than the metal element L; (c) n is 0.001 to 0.300 inclusive; and (d) the oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and particles of the oxide of the metal element L are deposited on the surfaces of particles of the oxide of the metal element N. The present invention also provides: a metal-supported product in which particles M of at least one metal selected from the group consisting of cobalt, iron and nickel are supported on the composite oxide; and an ammonia synthesis catalyst.

Description

[Technical field]

[0001] The present invention relates to a composite oxide useful for synthesizing ammonia under mild conditions, a metal-supported material and an ammonia synthesis catalyst using the same, a method for producing the composite oxide, a method for producing the metal-supported material, and a method for producing ammonia. [Background technology]

[0002] Ammonia is an important raw material in the modern chemical industry. More than 80% of the ammonia produced is used to manufacture chemical fertilizers for arable crops. In addition, ammonia has attracted much attention as an energy and hydrogen carrier because of (1) its high hydrogen content (17.6 wt%) and (2) its high energy density (12.8 GJ / m 3 ) and (3) no carbon dioxide is produced when it is decomposed to produce hydrogen. If it becomes possible to efficiently produce ammonia from renewable energy sources such as solar and wind power, it will help alleviate global problems related to energy and food crises.

[0003] The Haber-Bosch process currently used to produce ammonia is energy intensive, accounting for approximately 1-2% of the world's energy consumption. In this process, approximately 60% of the consumed energy is recovered and secured as the enthalpy of ammonia. However, most of the remaining energy is lost during the production of hydrogen from natural gas, during the synthesis of ammonia, and during gas separation. Because ammonia synthesis by the Haber-Bosch process is carried out at very high temperatures (>450°C) and pressures (>20MPa), there is a need to reduce the large amount of energy used in this process. To reduce global energy consumption, catalysts that can synthesize ammonia under milder conditions (lower temperatures and pressures) than the iron-based catalysts used in the Haber-Bosch process are needed.

[0004] In recent years, a method for producing ammonia under low pressure conditions of about 1 MPa (10 atm) has been known. The ruthenium catalyst used in ammonia production is generally supported on a carrier. For example, Patent Document 1 discloses that the amount of ruthenium used can be reduced and the reaction temperature can be lowered by using a rare earth oxide as a carrier for supporting ruthenium. However, the ammonia production method of Patent Document 1 does not provide a sufficient ammonia yield when ammonia is produced under lower pressure conditions. Therefore, the present inventors have developed a method for producing ammonia using La reduced at 650°C. 0.5 Ce 0.5 O 1.75 They developed a ruthenium catalyst using a support and reported that it showed excellent properties even under low pressure conditions (Non-Patent Document 4).

[0005] Furthermore, the present inventors have developed a binary composite oxide consisting of two types of metal elements, and a metal support (ammonia synthesis catalyst) in which a catalyst such as ruthenium is supported on the binary composite oxide (support) (Patent Document 5, Patent Document 6). The following is disclosed as an ammonia synthesis catalyst using the binary composite oxide (support) disclosed in these documents.

[0006] Ru / Ce 0.85 La 0.15 O x _(500℃, 600℃, 650℃, 700℃) Reduction, Ru / Ce 0.67 La 0.33 O x _(500℃, 600℃, 650℃, 700℃) Reduction, Ru / Ce 0.33 La 0.67 O x _(500℃, 600℃, 650℃, 700℃) Reduction, Ru / Ce 0.15 La 0.85 O x _(500℃, 600℃, 650℃, 700℃) Reduction, Ru / Ce 0.5 La 0.5 O x _(500℃, 650℃, 800℃) Reduction, Ru / Ce 0.5 Zr 0.5 O x _700℃ reduction, Ru / Ce 0.5 Pr 0.5O x _(500℃, 600℃, 650℃, 700℃, 800℃) Reduction, Ru / La 0.5 Pr 0.5 O x _(450℃, 500℃, 600℃, 650℃, 700℃) Reduction, Ru / Ba 0.1 La 0.9 O x _(500℃, 700℃, 800℃, 900℃) Reduction, Ru / Ba 0.1 Ce 0.9 O x _(500℃, 700℃) Reduction, Co / Ba 0.05 La 0.95 O x _(500℃, 600℃, 700℃, 800℃) Reduction, Co / Ba 0.01 La 0.99 O x _700℃ reduction, Co / Ba 0.03 La 0.97 O x _700℃ reduction, Co / Ba 0.1 La 0.9 O x _700℃ reduction.

[0007] Furthermore, this document also describes the reduction of 8.4wt%Ba / 4.5wt%Ru / MgO (500℃, 700℃) (Examples 80 and 81). These oxides were prepared by impregnating the support MgO with Ru solution, calcining it, and then supporting Ba with Ba(OH)2·8H2O.

[0008] In addition to Patent Document 1 and Non-Patent Document 4, various patent documents disclose ammonia synthesis catalysts in which ruthenium is supported on various rare earth oxide supports. Representative examples include Patent Documents 2 to 4 and Non-Patent Documents 1 to 3. Patent Document 2 and Patent Document 4 disclose lanthanide oxides as supports, Patent Document 3 discloses praseodymium oxide, and Non-Patent Document 1 discloses Ce oxide. Non-Patent Document 2 discloses a Ru / CeO2-La2O3-based catalyst produced by coprecipitating hydroxides of Ru, Ce, and La, drying and activating them.

[0009] Prior art documents including Patent Documents 1, 2, and 4 and Non-Patent Document 1 state that Ru exists as particles on the surface of the carrier of the ruthenium catalyst used in ammonia synthesis. When it exists as particles, it is reported that the average diameter is greater than 5 nm (see Non-Patent Document 2), and less than 2 nm (Non-Patent Document 4). Patent Document 3 also states that Ru has an eggshell structure. On the other hand, regarding the carrier, Non-Patent Document 3 describes that, in evaluating the ammonia synthesis activity of a Ru-supported Y(La)-MO (M is Ca, Sr, Ba) catalyst, the carrier oxide before Ru is supported has a large specific surface area when the support oxide is fired at 450°C, and the specific surface area of ​​the carrier with the fired temperature raised to 650°C is reduced. In addition, in view of the high cost of Ru, ammonia synthesis catalysts have been proposed in which a transition metal compound other than Ru, such as Co, is supported on a support (see, for example, Non-Patent Document 5 and Non-Patent Document 6). However, Non-Patent Document 6 discloses Co-BaO / C in which cobalt is supported on barium oxide, but the ammonia synthesis activity was low. In addition, Non-Patent Document 5 uses calcium amide instead of oxide (Co / Ba-Ca(NH2)2), but the ammonia yield at 1 MPa of the catalyst supporting Co was not as high as that of the catalyst supporting Ru. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 6-079177 [Patent Document 2] JP 2013-111562 A [Patent Document 3] International Publication No. 2016 / 133213 [Patent Document 4] JP 2017-018907 A [Patent Document 5] International Publication No. 2019 / 059190 [Patent Document 6] International Publication No. 2019 / 216304 [Non-patent literature]

[0011] [Non-Patent Document 1] Y. Niwa and K. Aika, Chemistry Letters, (1996) 3-4 [Non-Patent Document 2] X. Luo et al., Catalysis Letters 133, 382 (2009) [Non-Patent Document 3] ASIvanova et al., Kinetics and Catalysis, Vol. 45, No. 4, 2004, pp. 541-546. Translated from Kinetika i Kataliz, Vol. 45, No. 4, 2004, pp. 574-579. [Non-Patent Document 4] Y. Ogura et al., "Efficient ammonia synthesis over a Ru / La0,5Ce0.5O1.75 catalyst pre-reduced at high temperature", Chemical Science, Vol. 9, pp. 2230-2237. [Non-Patent Document 5] M. Kitano et al.,Angew. Chem. Int. Ed.,130(2018)2678 [Non-Patent Document 6] W. Gao et. al., ACS Catal., 7 (2017) 3654 Summary of the Invention [Problem to be solved by the invention]

[0012] Generally, catalysts for synthesis are required to have high synthesis activity. For ammonia synthesis catalysts, which are still under development, there is a continuing demand for high activity catalysts that enable higher yields. Among binary catalysts, for example, Co / BaLaOx Although such a catalyst has a sufficiently high ammonia synthesis activity, there is a demand for further improvement in activity.

[0013] The present invention aims to provide a composite oxide that, when carrying cobalt, exhibits higher ammonia synthesis activity than conventional rare earth-containing binary composite oxides, such as BaLaOx. Another object of the present invention is to provide a metal-supported material and a catalyst for ammonia synthesis that exhibit such high ammonia synthesis activity. Still another object of the present invention is to provide a method for producing such a composite oxide or metal-supported material, and a method for producing ammonia. [Means for solving the problem]

[0014] In order to solve the above problems, the present inventors have discovered that by using a combination of two types of Group 2 elements having specific properties as metal oxides constituting a composite oxide, the ammonia synthesis activity is high when used as a catalyst, and have made the following invention.

[0015] [1] A composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, the composite oxide being represented by the composition of the following general formula (1) and being characterized in that it is: L n N 1-n (1) (a) the metal element L is an oxide of an element selected from the following (i) to (iii): (i) Group 1 elements; (ii) Group 2 elements; (iii) Group 1 and Group 2 elements; (b) the metal element N is a Group 1 or Group 2 element other than the metal element L; (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) The oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the oxide particles of the metal element L are deposited on the surfaces of the oxide particles of the metal element N.

[0016] [2] (a) The metal element L is a partial negative charge of oxygen in the oxide state (-δ OA ) represents a strongly basic metal element having a value of 0.56 to 0.70, (b) The metal element N is a partial negative charge (-δ OB ) is 0.35 or more and 0.55 or less, which is a weakly basic metal element.

[0017] [3] A binary composite oxide consisting of a metal element A contained in a metal element L and a metal element B contained in a metal element N, wherein the general formula (1) is represented by the composition of the following general formula (2) and is characterized in that it satisfies the following (a) to (d): A n B 1-n (2) (a) The metal element A has a partial negative charge of oxygen in the oxide state (-δ OA ) represents a Group 2 element that is a strongly basic element with a value of 0.56 to 0.70, (b) The metal element B has a partial negative charge of oxygen in the oxide state (-δ OB ) represents a Group 2 element that is a weakly basic element with a value of 0.35 to 0.55, (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) The oxide of the metal element A and the oxide of the metal element B do not form a solid solution, and the oxide particles of the metal element A are deposited on the surfaces of the oxide particles of the metal element B.

[0018] [4] A composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, the composite oxide being represented by the composition of the following general formula (3) and being characterized in that it is: L n N 1-n O x (3) (a) the metal element L is an oxide of an element selected from the following (i) to (iii): (i) Group 1 elements; (ii) Group 2 elements; (iii) Group 1 and Group 2 elements; (b) the metal element N is a Group 1 or Group 2 element other than the metal element L; (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) The oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the oxide particles of the metal element L are deposited on the surfaces of the oxide particles of the metal element N.

[0019] [5] (a) The metal element L is a partial negative charge of oxygen in the oxide state (-δ OA ) represents a metal element that is a strongly basic element with a value of 0.56 to 0.70, (b) The metal element N is a partial negative charge (-δ OB ) is 0.35 or more and 0.55 or less, which is a weakly basic metal element.

[0020] [6] A binary composite oxide comprising a metal element A contained in a metal element L and a metal element B contained in a metal element N, wherein the general formula (3) is represented by the composition of the following general formula (4) and is characterized in that the following (a) to (d) are satisfied: A n B 1-n O x (4) (a) The metal element A is a partial negative charge of oxygen in the oxide state (-δ OA ) represents a Group 2 element that is a strongly basic element with a value of 0.56 to 0.70, (b) The metal element B has a partial negative charge of oxygen in the oxide state (-δ OB ) represents a Group 2 element that is a weakly basic element with a value of 0.35 to 0.55, (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element A and the oxide of the metal element B do not form a solid solution, and the oxide particles of the metal element A are deposited on the surfaces of the oxide particles of the metal element B; (e) The complex oxide according to [4] or [5], wherein x is the number of oxygen atoms required for the complex oxide to maintain electrical neutrality.

[0021] [7] Ba n Mg 1-n O x (wherein, 0.001≦n≦0.300).

[0022] [8] Ba n Mg 1-n O x (wherein, 0.01≦n≦0.10).

[0023] [9] The composite oxide according to [7] or [8], characterized in that the amount of carbonate contained in the composite oxide is 10 mol % or less relative to Ba.

[0024]

[10] A metal-supported material, comprising the composite oxide according to any one of [1] to [9] supported with at least one type of metal particles M selected from the group consisting of cobalt, iron and nickel.

[0025] [10-1] A metal support comprising the metal particles M and the composite oxide described in [1] to [3] above, each element being recognized as a particle aggregate, and a metal element L having a particle size 10% or less of the particle size of the metal particles M is observed to be distributed on the metal particles M, between the metal particles M and the metal oxide N, and on the metal oxide N. [10-2] The metal support according to the above [10-1], in which the distribution of the metal element L particles is recognized to be uniform. [10-3] The metal support according to [10-1] to [10-2], wherein the particles of the metal element L are also distributed in an intermediate layer between the metal particles M and the metal element N. [10-4] The metal support according to any one of [10-1] to [10-3], wherein the composite oxide is the composite oxide according to [6], the metal element A is selected from metal elements L, and the metal element B is selected from metal elements N.

[0026]

[11] The metal support according to

[10] , characterized in that the metal particles M are supported on an oxide of a metal element L deposited on a surface of an oxide of a metal element N, and oxide particles of the metal element L are deposited on the surfaces of the metal particles M.

[0027]

[12] The metal support according to

[10] , characterized in that oxide particles of the metal element N are distributed between the oxide particles of the metal element L and the metal particles M. [12-1] The composite oxide is the composite oxide according to [6], and the metal element A is selected from metal elements L and the metal element B is selected from metal elements N.

[0028]

[13] The metal support according to

[10] , wherein the metal particles M are cobalt particles.

[0029]

[14] A catalyst for ammonia synthesis, comprising the metal-supported material according to

[10] .

[0030]

[15] A method for producing a metal-supported material according to the above

[10] , comprising the following steps (a) to (d): (a) an immersion step of impregnating an N precursor containing the metal element N with an L precursor containing the metal element L; (b) a composite oxide calcination step of calcining the mixture at a temperature of 500° C. or higher to obtain a composite oxide carrier; (c) a supporting step of impregnating the composite oxide with a precursor of a compound containing the metal particles M to obtain an impregnated support; (d) calcining the impregnated support at a temperature of 400° C. or higher.

[0031] [15-1] A method for producing a metal-supported material according to the above

[15] , wherein the metal element A is selected from metal elements L, the metal element B is selected from metal elements N, and the method includes the following steps (a) to (d): (a) an immersion step of immersing a B precursor containing the metal element B in an A precursor solution containing the metal element A; (b) a composite oxide calcination step of calcining the mixture at a temperature of 500° C. or higher to obtain a composite oxide carrier; (c) a supporting step of impregnating the composite oxide with a precursor solution of a compound containing the metal particles M to obtain an impregnated support; (d) calcining the impregnated support at a temperature of 400° C. or higher. [15-2] The method for producing a metal-supported material according to the above

[15] or [15-1], characterized in that the step (b) is carried out in air. [15-3] The method for producing a metal-supported material according to the above

[15] or [15-1], characterized in that the step (d) is carried out in argon.

[0032]

[16] The method for producing a metal-supported material according to any one of

[15] to [15-3], further comprising step (e). (e) A reduction step of calcining the metal-supported material obtained in (d) at 500° C. or higher in the presence of hydrogen.

[0033]

[17] A method for producing ammonia by contacting hydrogen and nitrogen with a catalyst, wherein the catalyst is the ammonia synthesis catalyst according to

[14] . Effect of the Invention

[0034] According to the present invention, it is possible to provide a composite oxide that, when carrying cobalt, for example, exhibits higher ammonia synthesis activity than conventional binary composite oxides containing rare earth elements, for example Ru / BaLaOx. Also, according to the present invention, it is possible to provide a metal support and an ammonia synthesis catalyst that exhibit such high ammonia synthesis activity. Furthermore, according to the present invention, it is possible to provide a method for producing such a composite oxide or metal support, and a method for producing ammonia. [Brief description of the drawings]

[0035] [Figure 1]1 is a graph showing the ammonia synthesis activity of a Co / Ba0.01Mg0.99Ox_700°C reduced catalyst (a catalyst prepared by supporting Co and then reducing it at 700°C) in an example. [Diagram 2] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the amount of Ba added to the carrier in the Co / BaMgOx catalyst of the example. [Diagram 3] 1 is a graph showing the ammonia synthesis activity measured using a BaMgOx catalyst in which the amount of Ba added to the carrier is changed in a Co / BaMgOx catalyst of an example. [Figure 4] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the reduction temperature in the Co / BaMgOx catalyst of the example. [Diagram 5] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the reduction temperature in the Co / BaMgOx catalyst of the example. [Figure 6] 1 shows XRD patterns measured using Co / BaMgOx catalysts prepared by changing the reduction temperature in the Co / BaMgOx catalyst of the example. [Figure 7] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the amount of Co supported in the Co / BaMgOx catalyst of the example. [Figure 8] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the amount of Co supported in the Co / BaMgOx catalyst of the example. [Figure 9] 1 is a graph showing ammonia synthesis activity measured by changing the reaction pressure in a Co / BaMgOx catalyst of an example. [Figure 10] 1 is a graph showing ammonia synthesis activity measured by changing the reaction pressure in a Co / BaMgOx catalyst of an example. [Figure 11] 1 is a graph showing ammonia synthesis activity measured by changing the reaction pressure in a Co / BaMgOx catalyst of an example. [Figure 12]1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the pretreatment conditions in the Co / BaMgOx catalyst of the example. [Figure 13] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the Co precursor in the Co / BaMgOx catalyst of the example. [Figure 14] 1 shows XRD patterns measured using Co / BaMgOx catalysts prepared by changing the Co precursor in the Co / BaMgOx catalyst of the example. [Figure 15] 1 is a graph showing the ammonia synthesis activity measured by changing the SV in the Co / BaMgOx catalyst of the example. [Figure 16] 1 is a graph showing the ammonia synthesis activity measured by changing the SV in the Co / BaMgOx catalyst of the example. [Figure 17] 1 is a graph showing the ammonia synthesis activity measured at a low reaction temperature in the Co / BaMgOx catalyst of the example. [Figure 18] 1 is a graph showing the ammonia synthesis activity measured at a low reaction temperature in the Co / BaMgOx catalyst of the example. [Figure 19] 1 is a graph showing the ammonia synthesis activity of Ru / BaMgOx of an example. [Figure 20] 1 is a graph showing the ammonia synthesis activity of an Fe / Ba0.01Mg0.99Ox_700°C reduced catalyst (a catalyst prepared by supporting Co and then reducing at 700°C) in an example. [Figure 21] 1 is a graph showing the ammonia synthesis activity measured using Co / BaMgOx catalysts prepared by changing the pretreatment conditions in the Fe / BaMgOx catalyst of the example. [Figure 22] 1 is a graph showing the ammonia synthesis activity of a Co-Fe catalyst in a Co / BaMgOx catalyst of an example. [Figure 23] 1 shows the results of H2-TPR measurement of the Co / BaMgOx catalyst of Example 1. [Figure 24] 1 shows the results of H2-TPR measurement of the Co / MgOx catalyst of Comparative Example 2. [Diagram 25] 1 shows elemental mapping by TEM for the Co / BaMgOx catalyst of Example 1, including (1) an HAADF-STEM image, (2) elemental mapping of Ba, (3) elemental mapping of Mg, (4) elemental mapping of Co, and (5) an elemental map overlay of Ba, Co, and Mg. [Figure 26] 1 is a graph showing the ammonia synthesis activity of a catalyst in which Ba in the Co / BaMgOx catalyst of the example is replaced with another Group 2 element. [Figure 27] 1 is a graph showing the ammonia synthesis activity measured using a catalyst prepared by substituting a Group 1 element for a Group 2 element. [Figure 28] 1 is a graph showing the ammonia synthesis activity of a catalyst using a support prepared by adding both a Group 2 element and a Group 1 element. [Figure 29] 1 is a graph showing the ammonia synthesis activity of a catalyst using a support prepared by adding both a Group 2 element and a Group 1 element. [Diagram 30] 1 is a graph showing the ammonia synthesis activity of a catalyst using a support prepared by adding both a Group 2 element and a Group 1 element. [Diagram 31] 1 is a graph showing the ammonia synthesis activity of a catalyst using a support prepared by adding both a Group 2 element and a Group 1 element. [Diagram 32] 1 is a graph showing the ammonia synthesis activity of catalysts using supports prepared using various transition metal elements. [Diagram 33] 1 is a graph showing the ammonia synthesis activity of catalysts using supports prepared using various transition metal elements. [Diagram 34] 13 shows elemental mapping by TEM for the Co / BaMgOx catalyst of Example 17, including (1) an HAADF-STEM image, (2) elemental mapping of Ba, (3) elemental mapping of Mg, (4) elemental mapping of Co, and (5) an elemental map overlay of Ba, Co, and Mg. [Diagram 35] FIG. 2 is a diagram illustrating the structural features of the metal support of Examples 1 and 17. [Diagram 36] Normalized XANES spectra of the catalyst and standard sample. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] <Complex oxide> The composite oxide of the present invention is a composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, and is represented by the composition of the following general formula (1) and is characterized in that it is: L n N 1-n (1) It is. Here, the metal element L is an oxide of an element selected from any one of the following (i) to (iii): (i) Group 1 elements; (ii) Group 2 elements (iii) Group 1 and Group 2 elements. In the present invention, the "metal element L" includes not only one type of element (a Group 1 element or a Group 2 element) but also two types of elements (a Group 1 element and a Group 2 element). The Group 1 element as the metal element L is a metal called an alkali metal, and examples thereof include Li, Na, K, Rb, and Cs. The Group 2 element is a metal called an alkaline earth metal, and examples thereof include Be, Mg, Ca, Sr, Ba, and Ra. The metal element L may be a Group 1 element and a Group 2 element used simultaneously. These elements are selected with basicity in mind. Furthermore, the partial negative charge described below can be calculated and used. When using a Group 1 metal and a Group 2 metal, the ratio is preferably within the range of 0.1:1.9 to 1.9:0.1, more preferably within the range of 0.8:1.2 to 1.2:0.8, and particularly preferably 1:1. The metal element L is preferably a Group 2 element alone or a composite oxide of a Group 1 element and a Group 2 element, from the viewpoint of high ammonia synthesis activity of the metal support described below.

[0037] The metal element N is an oxide of a Group 1 or Group 2 element other than the metal element L. The metal element L is used in a small amount relative to the metal element N. The ratio of the metal element N to the total amount of metal elements of the metal element L is usually 0.001 to 0.300, preferably 0.01 to 0.100. The ratio of the metal element L affects the morphology during catalyst production and also affects the catalytic activity. The oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the metal element L is observed on the metal element N. In this specification, this state is sometimes referred to as the metal element L or the oxide of the metal element L being deposited on the metal element N or the oxide of the metal element N.

[0038] In the composite oxide used in the present invention, metal element A is selected from metal elements L, and metal element B is selected from metal elements L. When this is a binary composite oxide, general formula (1) is represented by the following general formula (2). A n B 1-n (2) (a) The metal element A is an alkaline earth metal of Group 2, and has a partial negative charge of oxygen in the oxide state (-δ OA ) is a strongly basic element with a value of 0.56 or more and 0.70 or less. (b) The metal element B is an alkaline earth metal other than the metal element A, and has a partial negative charge of oxygen in the oxide state (-δ OB ) represents a Group 2 element that is a weakly basic element with a value of 0.35 or more and 0.55 or less. (c) The ratio of the metal element A to the total amount is 0.001 or more and 0.300 or less, and the morphology in this range has a positive effect on the catalytic activity. (d) In addition, in this specification, a state in which the oxide of metal element A and the oxide of metal element B do not form a solid solution and the oxide particles of metal element A and the oxide particles of metal element B are observed on the surface is expressed as being "deposited".

[0039] The composite oxide represented by the composition of the following general formula (1) can be written in another way as formula (3). That is, the composite oxide used in the present invention is a composite oxide consisting of an oxide of a metal element L and an oxide of a metal element N, and is represented by the composition of the following general formula (3) and is characterized by the following (a) to (d): L n N 1-n O x (3) (a) the metal element L is an oxide of an element selected from the following (i) to (iii): (i) Group 1 elements; (ii) Group 2 elements; (iii) Group 1 and Group 2 elements; (b) the metal element N is a Group 1 or Group 2 element other than the metal element L; (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the oxide particles of the metal element L are deposited on the surfaces of the oxide particles of the metal element N; (e) The above-mentioned x is the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality. The composite oxide of the present invention is a binary composite oxide consisting of a metal element A and a metal element B, represented by the composition of the following general formula (4), which is an alternative expression of the above general formula (2). A n B 1-n O x (4) (Here, A, B, n, and x are as explained in the above general formula (2).)

[0040] <Basic> In the composite oxide used in the present invention, the oxide of the metal element L and the oxide of the metal element N do not form a solid solution. The metal element L is a partial negative charge of oxygen in the oxide state (-δ OA The metal element N is preferably a strongly basic element having a partial negative charge (-δ) of oxygen in the oxide state of 0.56 to 0.70. OBPreferably, the metal element is a weakly basic element having a value of 0.35 or more and 0.55 or less.

[0041] When metal element A is selected from metal elements L and metal element B is selected from metal elements N, and a binary composite oxide is formed, (a) The metal element A has a partial negative charge of oxygen in the oxide state (-δ OA ) represents a Group 2 element that is a strongly basic element with a value of 0.56 to 0.70, (b) The metal element B has a partial negative charge of oxygen in the oxide state (-δ OB ) represents a Group 2 element that is a weakly basic element with a value of 0.35 to 0.55, (c) said n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element A and the oxide of the metal element B do not form a solid solution, and the oxide particles of the metal element A are deposited on the surfaces of the oxide particles of the metal element B; (e) The above-mentioned x is the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality.

[0042] Metal element A is the partial negative charge of oxygen in the oxide state (-δ O ) is a strongly basic element with a value of 0.56 to 0.70. OA The value is more preferably 0.60 or more, and most preferably 0.65 or more. Specifically, the metal element A can be selected from Ba (barium), Sr (strontium), and Ca (calcium).

[0043] Metal element B is the partial negative charge of oxygen in the oxide state (-δ O ) is a weakly basic element with a value of 0.35 to 0.55. OB The value of -δ is more preferably 0.40 or more. OB The value is more preferably 0.50 or less, and most preferably 0.45 or less. Specifically, the metal element B can be selected from Mg (magnesium) and Be (beryllium). -δ OA and -δ OBThe difference between is preferably 0.10 to 0.40, more preferably 0.15 to 0.35, and most preferably 0.20 to 0.30.

[0044] In the present invention, since the metal element A contained in the composite oxide is a strongly basic element that exhibits high basicity in the oxide state, it is possible to improve the activity of the ammonia synthesis catalyst. The following is an outline of the mechanism.

[0045] Metal element A is a strongly basic metal element. Electrons are generated from the base points of the composite oxide (support) of this element, and are donated back to nitrogen molecules via transition metal particles, which are the catalyst supported on the composite oxide, weakening the nitrogen triple bond. The inventors consider this step to be the rate-determining step of the ammonia synthesis reaction, and believe that the above-mentioned series of electron movements reduces the energy required to break the triple bond of the nitrogen molecule, thereby improving the ammonia synthesis activity of the metal support (catalyst).

[0046] The basicity (Lewis basicity) of metal oxides is related to the level of their electron donating ability. In other words, it is thought that the higher the electron donating ability of a substance, the stronger its basicity. Basically, oxygen acts as an electron donor in oxides, so the amount of charge that oxygen in an oxide has, that is, the partial negative charge of oxygen, is a useful indicator of basicity. In fact, a non-patent document (Sanderson, Inorganic Chemistry (Vol. 1), Hirokawa Shoten (1975), p. 276, Table 12.7) shows that the value of the partial negative charge of oxygen correlates well with the acid-base property of an oxide.

[0047] Here, for the oxides of individual metal elements, the partial negative charge of oxygen (-δ O ) can be calculated using the values ​​listed in Table 12.7 of the non-patent literature (Sanderson, "Inorganic Chemistry (Vol. 1)", Hirokawa Shoten, 1975, p. 276). If the value is not listed, it can be calculated using the partial negative charge of oxygen described above. The table below shows the partial negative charge of oxygen (-δ O ) value.

[0048] [Table 1]

[0049] On the other hand, for the calculation method of the partial negative charge of oxygen for the entire composite oxide, we referred to a non-patent document (Sanderson, "Inorganic Chemistry (Vol. 1)," Hirokawa Shoten (1975), p. 122, table 6.7, p. 126-128). First, the composition ratio of each element in the composite oxide is calculated. For example, "Ce 0.5 La 0.5 O 1.75 For La, the value is 0.5. Let this value be ni (i is the corresponding element). Let the electronegativity of each element be χi. The geometric mean of the electronegativity of all atoms that make up the composite oxide is (Π(χi ni ))^(1 / Σni). Next, to determine the change in oxygen electronegativity, take the difference between the geometric mean and the electronegativity of oxygen (5.21). Finally, divide the change in oxygen electronegativity by the change in electronegativity when one oxygen atom gains one electron (-4.75). Using these calculations, the partial negative charge of oxygen exhibited by the complex oxide can be calculated.

[0050] To summarize the above, the value of the partial negative charge of oxygen in a complex oxide is expressed by the following formula (A) when the composition ratio of each element contained in the complex oxide is ni (i = all elements in the complex oxide containing at least A, B, O) and the electronegativity of each element is χi (i = all elements in the complex oxide containing at least A, B, O). ((Π(χi ni ))^(1 / Σni)―5.21) / -4.75 ··Eq. (A)

[0051] When determining the partial negative charge of oxygen in a complex oxide, (a) the partial negative charge of oxygen in the oxide state among the elements that form the complex may be used, or (b) the composition ratio of each element contained in the complex oxide is ni (i=all elements in the complex oxide including A, B, and O) and the Sanderson electronegativity of each element is χi (i=all elements in the complex oxide including A, B, and O) and it may be determined by the following formula (A). ((Π(χi ni))^(1 / Σni)―5.21) / -4.75 ··Eq. (A) When the composite oxide forms a homogeneous composite oxide, it is preferable to carry out the calculation by the method (b). On the other hand, when the composite oxide forms a heterogeneous composite oxide, it is preferable to carry out the calculation by the method (a), and in this case, the result of the element with the largest absolute value of partial negative charge of oxygen of the individual elements is used. In the composite oxide of the present invention, the oxide of metal element A and the oxide of metal element B are phase-separated without forming a solid solution, so that the value of partial negative charge of oxygen of the composite oxide is preferably calculated by the above method (a).

[0052] The partial negative charge value of oxygen in the composite oxide is preferably 0.35 or more, more preferably 0.40 or more. When the partial negative charge value of oxygen in the composite oxide is 0.35 or more, the ammonia synthesis activity tends to be high.

[0053] <Removal of carbonates and hydroxides> Metal elements L (alkali metals) and N (alkaline earth metals), even in the form of oxides, are highly basic and easily react with carbon dioxide or water in the atmosphere to become metal carbonates or hydroxides. However, these metal carbonates and hydroxides reduce the basicity of the composite oxide, causing a decrease in the ammonia synthesis activity of the catalyst. For example, Ba becomes BaCO3 or Ba(OH)2 in the atmosphere, which reduces the ammonia synthesis activity. Therefore, it is preferable that the amount of metal carbonates and hydroxides contained in the ammonia synthesis catalyst is as small as possible. In order to reduce the amount of metal carbonates and hydroxides, it is preferable to perform a reduction treatment under heating conditions as described below, which decomposes the metal carbonates and hydroxides contained in the catalyst and prevents a decrease in basicity. The amount of carbonate contained in the metal support is not particularly limited as long as it is within a range that does not inhibit the ammonia synthesis activity, and is, for example, 10 mol% or less, preferably 1 mol% or less, more preferably 0.1 mol% or less, and even more preferably 0.01 mol% or less relative to the metal element A.

[0054] The amount of carbonate present as metal carbonate can be quantified by heating a catalyst under a hydrogen flow, hydrogenating the carbonate species, and detecting the generated hydrocarbons such as methane using a mass spectrometer, a flame ionization detector (FID), a thermal conductivity detector (TCD), or the like, and converting the amount.

[0055] Alternatively, infrared absorption spectroscopy, which has high sensitivity to metal carbonates, can be used. The amount of carbonate contained in the catalyst can be quantified by irradiating the catalyst with infrared light and measuring the absorption intensity of the peak wavenumber at which carbonates characteristically absorb. For example, the position of the peak that can be used to quantify barium carbonate is 3000 cm. -1 Near, 2450cm -1 Near 1750cm -1 Near, 1480cm -1 Near, 1060cm -1 Nearby areas, etc.

[0056] The table below shows the melting points of oxides of Ba and Sr, which are Group 2 elements with large partial negative charge on oxygen, and the alkali metals Cs and K.

[0057] [Table 2]

[0058] Based on the H2-TPR measurement results described below, it is believed that the following reaction occurs: BaCO3+ 4H2→ BaO +CH4+ 2H2O (5) In addition, although the oxide of Ba has a high melting point, as described above, it passes through a hydroxide with a low melting point during heat treatment under a hydrogen atmosphere. Therefore, the hydroxide melts and acquires fluidity. At this time, since both Ba and metal element B exist as strongly basic compounds, they repel each other, or due to interfacial tension, or for some other reason, as a result, the Ba compound flows onto the metal particles, and a state in which the hydroxide of Ba is distributed in particulate form on the surface of the metal particles is generated, and after the reaction, it becomes an oxide, loses fluidity, and shrinks in volume, so that it is fixed in this state with voids, thereby exhibiting high activity. In the present invention, the state in which it further exists in particulate form on the metal surface is called a "distributed" or "accumulated" state.

[0059] Thus, Ba is particularly preferable as the metal element A, since the element has a strong inherent basicity and it is easy to reduce the amount of carbonate that inhibits it, and therefore Ba can increase the ammonia synthesis activity.

[0060] The oxide of the metal element B is the main component of the composite oxide, and in the present invention, it exhibits weak basicity (including weakly basicity; the same applies in the following description). n La 1-n O x In the present invention, the partial negative charge value of the oxide of the metal element B is low, ranging from 0.35 to 0.55, whereas the two metal elements Ba and La have high partial negative charge values ​​of the oxide (Ba is 0.67 and La is 0.56).

[0061] <Deposition> In the present invention, the oxide of metal element L and the oxide of metal element N are separated into phases without forming a solid solution, and the oxide of metal element L is deposited on the surface of the oxide particles of metal element N, and moreover, is deposited on the surface of the metal particles on which the oxide of metal element L is supported. Therefore, even if the basicity of the oxide of metal element N is weak, if the basicity of the oxide of metal element L is strong, the ammonia synthesis activity is increased by the oxide of metal element L. Therefore, even if the oxide of metal element N is lower than before, high ammonia synthesis activity is exhibited.

[0062] The oxide of the metal element N is preferably one with a large specific surface area (SSA). This is because, if the oxide of the metal element N, which is the main component of the composite oxide, has a large specific surface area, fine nanoparticles such as Co can be firmly fixed, and the number of active sites of these nanoparticles increases, resulting in high ammonia synthesis activity. Therefore, from the viewpoint of the size of the specific surface area, Mg (magnesium) is particularly preferable as the metal element N. Although the metal element N is the main component of the composite oxide, when it is used as a catalyst as a support with a transition metal, the oxide of the metal element N plays a large role as a support.

[0063] From the above viewpoint, the composite oxide of formula (1) and formula (2) is Ba n Mg 1-n O x (wherein 0.001≦n≦0.300) is preferred.

[0064] Here, Ba n Mg 1-n O x In the above, the composition ratio of Ba (i.e., the value of n) is preferably within the range of 0.01≦n≦0.10. As shown in the examples described later, when n is within the range of 0.01≦n≦0.10, ammonia synthesis activity (yield, amount) tends to be high.

[0065] <Metal carrier> The metal support of the present invention is a composite oxide of the present invention carrying particles of a transition metal other than Group 4 (hereinafter, sometimes referred to as transition metal particles). From the viewpoint of high catalytic activity, the transition metal is preferably one or more selected from the group consisting of Ru, Fe, Co, Ni, Rh, Pd, Os, Ir, and Pt, and more preferably Ru, Co, or a mixture of Fe and Co. Among these, Co is particularly preferred because of the high ammonia synthesis activity when combined with the composite oxide of the present invention. The quantitative ratio of the transition metal to the composite oxide can be determined in consideration of the catalytic activity and the cost of the transition metal. For example, the ratio of the transition metal to the entire metal support is preferably in the range of 0.1 to 50% by weight, more preferably in the range of 5.0 to 30% by weight.

[0066] The transition metal M of the present invention does not form a solid solution with either the oxide of the metal element L or the oxide of the metal element N. In particular, it is preferable that the structure in which the oxide particles of the metal element L are deposited and covered on the particles of the transition metal M is further deposited on the surface of the oxide particles of the metal element N, which is the main component. That is, it is preferable that the transition metal M is the core and the metal element N is the shell, so-called core / shell relationship. It is preferable that the entire transition metal M is covered by the oxide particles of the metal element L, and is supported on the oxide particles of the metal element N, which is the support, via the oxide of the metal element L. It is considered that such a structure is due to the fact that the oxide of the metal L, which has fluidity, covers the transition metal M during the high-temperature reduction treatment after the metal N supports the metal L and then the transition metal M is supported on the metal N. If the amount of the metal L is too large relative to the amount of the metal element N, which is the support, or too large relative to the amount of the transition metal, the layer becomes too thick, which is undesirable because nitrogen and hydrogen cannot reach the transition metal surface, which is the active site. Furthermore, firing at a high temperature exceeding 700° C. or for a long period of time is undesirable because it causes the oxide particles of metal L to aggregate, preventing nitrogen and hydrogen from reaching the transition metal surface, which is an active site.

[0067] The composite oxide of the present invention is in a mixed state of an oxide of metal element L and an oxide of metal element N. In particular, it is preferable that the composite oxide has a laminated structure in which oxide particles of metal element L are deposited on the surface of oxide particles of metal element N, which is the main component. It is most preferable that the two have a so-called core / shell relationship. Furthermore, the metal element L does not have to be present inside the catalyst carrier, and it is preferable that the metal element L is present on the carrier surface. In particular, the composite oxide of the present invention is in a mixed state of an oxide of metal element A and an oxide of metal element B. In particular, it is preferable that the composite oxide has a laminated structure in which oxide particles of metal element A are deposited on the surface of oxide particles of metal element B, which is the main component. It is most preferable that the two have a so-called core / shell relationship. Furthermore, metal element A does not have to be present inside the catalyst carrier, and metal element A is preferably present on the carrier surface.

[0068] Since the oxide of metal element L and the oxide of metal element N are not in a solid solution but in a mixed state (phase separation), when the oxide is made into a metal support (catalyst) as described below, the transition metal particles come into direct contact with the oxide of metal element L on the surface of the composite oxide. Since the oxide of metal element L (e.g. Ba) is strongly basic, it is presumed that direct contact of transition metal particles with these oxides increases the number of active sites that exhibit high activity, resulting in higher ammonia synthesis activity. On the other hand, in the case of Co, the basicity of the cation is important, and the oxide of metal element A such as Ba with a larger partial negative charge on oxygen has higher ammonia synthesis activity.

[0069] The particle size ratio A / M of the oxide particles of metal element A to the metal particles M is usually 20% or less, preferably 10% or less, and more preferably 5% or less. In order to change this particle size, the ratio of metal element A to transition metal M is adjusted. If this particle size ratio is too large or too small, it tends to be difficult to obtain the expected catalytic activity.

[0070] In addition, the Co dispersion value (D ads ) and the Co dispersion predicted from the average particle size of Co particles obtained from the TEM image (D TEM ) is 0 <Dads / D TEM It is preferable that the ratio is <1. The Co dispersion degree represents the ratio of the number of Co atoms exposed on the surface of the metal support to the number of all Co atoms contained in the metal support. The Co dispersion degree can be determined from the amount of hydrogen adsorbed on the metal support on which Co is supported.

[0071] Specifically, assuming that one Co atom adsorbs one H atom, the ratio (H / Co) of the number of hydrogen atoms H, which corresponds to the number of Co atoms exposed on the metal support surface, to the total number of Co atoms supported on the metal support is the Co dispersion. In the present invention, the Co dispersion based on the amount of hydrogen adsorption is called D ads By comparing metal supports with the same amount (same number of atoms) of Co supported, it can be considered that the higher the Co dispersion, the greater the number of catalytic active sites.

[0072] It is also known that, assuming that the morphology of Co particles is cubic, the value of Co dispersion can be geometrically calculated using the average particle diameter (d, unit: nm) of Co determined by TEM observation (see the literature "Dictionary of Catalysts"). The calculation method can be expressed by general formula (8). The average particle diameter of Co can be calculated by randomly extracting 100 to 150 Co particles from a TEM image, measuring the particle diameter of each, and averaging the measured values. In the present invention, the value of Co dispersion calculated based on general formula (4) is defined as D TEM It is written as follows. D TEM = 0.732 / d (8)

[0073] Therefore, D ads / D TEM The fact that the value of the metal element B is less than 1 means that a part of the Co particles, mainly near the interface between the particle and the composite oxide (support) and the particle surface, are covered with the oxide of metal element B, preventing the adsorption of H atoms onto the Co particle surface.

[0074] TOF (catalyst turnover frequency) refers to the number of reactions that occur on one active site on the catalyst surface per unit time. In this application, it is expressed as the number of ammonia molecules generated per second per one surface Co atom, which is an active site.

[0075] The average particle size of Co supported on the composite oxide is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 20 nm or less. The smaller the particle size of Co, the more advantageous it is because the number of active sites increases when used as an ammonia synthesis catalyst. There is no particular limit to the lower limit of the average particle size of Co, but it is, for example, 0.5 nm or more, 1 nm or more.

[0076] The metal-supported material of the present invention is made up of fine particles of supported metallic cobalt with an average particle size of 100 nm or less, which allows the material to exhibit a very high ammonia synthesis rate under mild ammonia synthesis conditions (300 to 500°C, 0.1 to 20 MPa).

[0077] In this specification, for the sake of simplicity, the term "Co-supported Ba 0.01 Mg 0.99 O 1.00 The metal carrier represented by "Co / Ba 0.01 Mg 0.99 O1" and the metal carrier that has been subjected to reduction treatment is referred to as "Co / Ba 0.01 Mg 0.99 O x The same expression will be used for other supports. Here, x means that the molar ratio of oxygen at the time of calcination, 1.00, has decreased to x due to reduction. In this specification, ABO is simply used. x When you write "A" and "B", it means that the ratio of A and B is not specified. 1.00 B 1.00 O x This does not mean that the

[0078] In the general formula (2) representing the proportion of oxygen O in the composite oxide, x is the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality. Although x depends on the types of elements A and B, it generally falls within the range of 0.5 < x ≤ 2, and particularly within the range of 0.9 < x ≤ 1.

[0079] <Effect of Reduction Temperature on Ammonia Synthesis Activity> The catalyst of the present invention is activated by performing a hydrogen reduction pretreatment at a high temperature. This is because Co is reduced. At this time, a characteristic structure in which the oxide of metal element A is deposited on the surface of Co particles is also manifested. Generally, when the reduction pretreatment is at a high temperature, a decrease in specific surface area accompanied by sintering of the carrier and coarsening of metal particle size occur, leading to a decrease in catalyst activity.

[0080] Figures 4 and 5 are graphs showing the ammonia synthesis activity of catalysts produced by changing the reduction temperature in the examples (Co / BaMgO x ) described later. From this graph, it can be seen that as the reduction temperature increases, the ammonia synthesis activity increases, and the ammonia synthesis rate is the highest when reduced at 700 °C and 800 °C. When reduced at 900 °C, the ammonia production rate is slightly lower compared to 800 °C.

[0081] Figure 6 shows the XRD pattern of Co / BaMgO in the examples described later. x As can be seen from this figure, before reduction, peaks due to BaCO3 were observed. When the reduction temperature is increased to 700 °C or higher, the peaks of BaCO3 disappear, indicating that BaCO3 is decomposed. It can also be seen that when the reduction temperature is increased, the peaks of Co increase.

[0082] Also, as shown in Figure 12, it was found that the catalyst reduced at 500 °C for 72 hours exhibits performance comparable to that of the catalyst reduced at 700 °C for 1 hour. From this, it can be seen that for the catalyst of the present invention, high activity can be obtained with a long time at low temperature reduction or a short time at high temperature reduction.

[0083] As the reduction temperature increases, TOF (catalyst turnover frequency) tends to increase.

[0084] In other words, the reason why the ammonia production rate decreases when the reduction temperature becomes higher than 800°C is thought to be that the support particles are sintered and enlarged, reducing the specific surface area and promoting sintering of Co, and that the surfaces of the Co particles are excessively covered with the oxide of metal element A, reducing the number of active sites.

[0085] By using a metal carrier carrying Co as a catalyst, ammonia can be produced by reacting nitrogen with hydrogen. The method for synthesizing ammonia itself is not particularly limited, but for example, ammonia can be produced by supplying a raw material gas consisting of hydrogen gas and nitrogen gas into a reaction vessel loaded with a catalyst. The reaction temperature is preferably 300 to 550°C, more preferably 300 to 500°C, and even more preferably 300 to 450°C.

[0086] When ammonia synthesis is performed using the catalyst of the present invention, the reaction pressure is preferably 0.1 to 20 MPa, which is a low pressure, more preferably 0.1 to 15 MPa, and even more preferably 0.1 to 10 MPa. As shown in Figs. 10 and 11, it can be seen that the catalyst supporting Co has improved activity even under high-pressure reaction conditions compared to the catalyst supporting Ru. This is because Co is less susceptible to hydrogen poisoning compared to Ru, and therefore its activity is less likely to decrease even under high pressure. That is, in the case of Ru, the interaction between the hydrogen atoms adsorbed on the surface and Ru becomes stronger under high pressure, making it significantly more difficult for hydrogen atoms to be desorbed, blocking the active points on the Ru surface, and making it difficult for the ammonia synthesis reaction that starts when nitrogen molecules are adsorbed to the active points to occur. Co has a weaker interaction with hydrogen compared to Ru, so this phenomenon is less likely to occur, and it has the property of being less likely to decrease in ammonia synthesis activity even under high pressure. In general, the ammonia synthesis reaction tends to increase the ammonia yield at higher pressures due to thermodynamic equilibrium, so it is expected that a higher yield can be obtained under high-pressure conditions, for example, about 10 MPa, by using the ammonia synthesis catalyst of the present invention. In addition, Co is widely distributed in the earth's crust, with an abundance 10,000 times that of Ru, making it more versatile and less expensive than Ru.

[0087] When using a metal carrier carrying Co as a catalyst, it is preferable from the viewpoint of catalytic activity that the composite oxide serving as the carrier contains Ba. With this combination, sufficient ammonia synthesis activity is exhibited even when Co, which is cheaper than Ru, is used. In addition, even when the reaction pressure is high, it is less susceptible to hydrogen poisoning than the Ru catalyst. Therefore, the reaction pressure is most preferably 1 to 10 MPa.

[0088] <Manufacturing method of composite oxides and metal supports> Next, a method for producing the composite oxide and metal-supported material of the present invention will be described. The composite oxide of the present invention can be produced by the following method. (a) an immersion step of impregnating an L precursor containing a metal element L into an N precursor containing a metal element N; (b) a composite oxide calcination step of calcining the mixture at a temperature of 500° C. or higher to obtain a support made of a composite oxide. The metal-supported material of the present invention can be produced by subjecting the composite oxides obtained in the above (a) and (b) to the following method. (c) a supporting step of impregnating the composite oxide with a precursor of a compound containing the metal particles M to obtain an impregnated support; (d) a support calcination step of calcining the impregnated support at a temperature of 400° C. or higher.

[0089] Step (a) will be described below. Step (a) corresponds to the method for producing a composite oxide of the present invention. The composite oxide is produced by mixing and impregnating an L precursor containing a metal element L and an N precursor containing a metal element N to obtain a mixture (precursor of the composite oxide). The precursor of the composite oxide can be prepared by various methods such as precipitation method, complex polymerization method, etc. For example, the neutralization precipitation method can be used, in which a precipitant such as ammonia, sodium hydroxide, or cesium hydroxide is reacted with the nitrate, chloride, acetate, carbonate, or sulfate of A or B to obtain the hydroxide.

[0090] The precursor of the composite oxide can also be obtained by separately preparing and mixing compounds containing one or more of the metal element L and the metal element N. In this manner, a mixture is obtained by mixing a compound containing the metal element L and a compound containing the metal element N.

[0091] Next, step (b) will be described. This step is a step of calcining the mixture obtained in step (a). By calcining, the mixture (composite oxide precursor) produced is converted into a complex oxide with a high specific surface area. The firing is preferably carried out at a low temperature of about 200 to 400° C. for about 1 to 10 hours, at an intermediate temperature of about 400 to 600° C. for about 1 to 10 hours, and at a high temperature of about 600 to 700° C. for about 1 to 10 hours. The firing temperature in the final step is most preferably 700° C. This firing can be carried out under any oxygen concentration in an atmosphere containing oxygen, such as in air or a mixed gas of oxygen and an inert gas.

[0092] Step (c) is described below. In step (c), the composite oxide obtained in step (b) is stirred with a solvent in which a transition metal particle source such as cobalt, iron, or nickel is dissolved, thereby impregnating the composite oxide with the transition metal particle source, and then the solvent is removed by heating, followed by decomposition of the transition metal particle source, thereby obtaining a pre-reduction treatment supported material in which the transition metal particles are supported in the form of fine particles on the composite oxide support.

[0093] As the transition metal particle source (cobalt source) of cobalt, various compounds containing Co can be used, for example, organometallic compounds such as acetylacetonatocobalt(II). Among these, acetylacetonatocobalt(II) is particularly preferred from the viewpoint of high ammonia synthesis activity. It is also possible to use other cobalt sources that can support cobalt on the composite oxide, such as cobalt nitrate, cobalt chloride, and nitrosyl cobalt nitrate.

[0094] When an organometallic compound such as cobalt(II) acetylacetonate is used as the cobalt supply source, it is advantageous to use an organic solvent as the solvent. Examples of organic solvents include tetrahydrofuran (THF), methanol, ethanol, hexane, and toluene. These solvents can be used without any pretreatment if they are general commercial products, but it is more preferable to use those that have been purified, dehydrated, etc. The solid content concentrations of the composite oxide and the cobalt supply source per liter of solvent are generally about 1 to 30 g / liter and about 0.1 to 3 g / liter, respectively, and more preferably about 10 to 30 g / liter and about 0.1 to 0.3 g / liter, respectively. Stirring can be performed at room temperature, and the stirring time is preferably 1 to 24 hours, and more preferably 6 to 12 hours. The removal of the solvent can be performed by heating using various methods, but it is preferable to perform the removal in a reduced pressure, low temperature atmosphere using an evaporator, etc. The decomposition of the cobalt supply source is performed by heating in an inert atmosphere, for example, a helium, argon, or nitrogen atmosphere. It can also be performed in an atmosphere containing hydrogen. Heating is carried out at a temperature of about 200 to 600° C. for about 1 to 12 hours. A more preferred heating temperature is about 300 to 500° C., and a more preferred heating time is about 3 to 6 hours.

[0095] As the ruthenium supply source, various compounds containing Ru can be used. Preferably, organometallic compounds such as triruthenium dodecacarbonyl and ruthenium acetylacetonate can be used. Other ruthenium supply sources that can support ruthenium on the composite oxide, such as ruthenium chloride and ruthenium nitrosyl nitrate, can also be used.

[0096] Step (d) will be described below. Next, the thus obtained pre-reduction treatment support (impregnated support) is subjected to reduction treatment. The reduction treatment is carried out for the purpose of reducing transition metal particles and reducing carbonates for destruction, which will be described later. The reduction temperature is 400°C to 800°C, and preferably 600 to 700°C. When the reduction temperature is a high temperature of more than 500°C, the reduction time is usually 10 minutes to 40 hours, and preferably about 30 minutes to 5 hours. When the reduction temperature is a low temperature, the reduction time is 48 hours to 120 hours, and preferably 60 hours to 100 hours. The reduction treatment is carried out in the presence of a reducing gas such as hydrogen gas.

[0097] It is known that when BaO contains strong basicity Ba, it reacts with carbon dioxide in the air and easily forms barium carbonate (Ba(CO3)) or barium hydroxide (Ba(OH)2). When carbonate or hydroxide is formed in this way, the partial negative charge of the oxygen in BaO is significantly reduced, and high basicity cannot be obtained. Therefore, in order to achieve high ammonia synthesis activity, it is necessary to destroy the carbonate or hydroxide by appropriate treatment. For example, a method for destroying Ba carbonate to turn it into BaO is heat treatment (reduction treatment) under a flow of hydrogen gas. This reaction is expressed by the following formula. BaCO3+ 4H2→ BaO +CH4+ 2H2O (5)

[0098] By heating the catalyst in a hydrogen atmosphere, hydrogen dissociates on the surface of the supported metal species, generating hydrogen species with strong reducing power. The action of these hydrogen species destroys the barium carbonate, converting it into BaO. An example of a method for destroying barium carbonate is to hold the catalyst under a hydrogen flow for about 1 hour at a temperature of 550°C or higher. The preferred conditions are about 600°C to 800°C. Barium carbonate can also be destroyed by holding the catalyst in a hydrogen stream at low temperatures for a long period of time. Preferred conditions are 500°C for about 48 hours, 450°C for about 72 hours, and 400°C for more than 120 hours.

[0099] By using such a method, the carbonate of Ba can be destroyed. In order to express the basic properties of Ba, it is desirable to reduce the proportion of Ba present as a carbonate as much as possible. The proportion of Ba present as a carbonate in the catalyst is preferably 10 mol % or less, more preferably 1 mol % or less, even more preferably 0.1 mol % or less, and particularly preferably 0.01 mol % or less, relative to the total amount of Ba contained in the catalyst.

[0100] The calcination temperature in step (d) is most preferably 700 to 800° C. If the calcination temperature in this step is too high, excessive sintering of the support and active metal occurs during the reduction treatment, and the particle size increases, reducing the number of active sites and decreasing the catalytic performance. On the other hand, if the calcination temperature in this step is too high, the specific surface area of ​​the support becomes small, the dispersion state of the active metal becomes poor, and the particle size becomes large, which reduces the number of active sites and reduces the catalytic performance. Regarding the relationship between the calcination temperature and the reduction temperature, as described above, from the viewpoint of ammonia synthesis activity, it is preferable to calcinate the support at a temperature approximately equal to or higher than the reduction treatment temperature.

[0101] FIG. 35 explains the above circumstances. FIG. 35 explains the difference due to the difference in the manufacturing method of the metal support Co / BaMgOx. In a previous study, the inventors disclosed Ba / Ru / MgO (see Examples 80 and 81 of WO2019 / 059190), but if the manufacturing method at that time is carried out in the present application, it will be as follows. That is, Co is supported on Ba to form FIG. 35(1), and barium is further supported to form (2), and then, for example, when reduced at a high temperature of 700°C, the structure of (2) is generated. That is, a structure is formed in which the transition metal Co is deposited on the support MgO, and barium oxide is deposited on that, but according to the cross section (3), Co and MgO are in direct contact with each other.

[0102] On the other hand, when a metal-supported material is produced by the method of the present invention, it becomes as follows. That is, BaO is supported on MgO, and then Co is supported, resulting in (4). Then, when (4) is reduced at, for example, 700°C, (5) is produced. This is because the supported Ba compound acquires fluidity during the high-temperature reduction treatment and moves to cover the Co. Therefore, when observing the cross section (6), MgO and Co are not in direct contact, and Co is arranged with MgO via the Ba compound. Barium oxide covers Co with a moderate density, so nitrogen and hydrogen can reach the Co, which is the active site.

[0103] The metal-supported material according to the present invention thus obtained is easier to handle and has better stability during the reaction than the metal-supported materials that have been used so far as catalysts for ammonia synthesis.

[0104] In addition, when Ba or the like is contained in the composite oxide, even if the catalyst is in an oxidized state during production, it is likely to absorb CO2 and become carbonate when exposed to the atmosphere. Therefore, after decomposing Ba carbonate by the above-mentioned reduction treatment, it is preferable to handle the catalyst so as not to expose it to CO2 until it is used, and it is preferable to store the catalyst by sealing it in a container filled with an inert gas, for example. However, even if a part of the support becomes carbonate, it is possible to reduce the carbonate and recover the ammonia synthesis activity by decomposing it by hydrogenation.

[0105] Metal supports used as catalysts in synthesis reactors must be replaced periodically and are expected to be used for a long period of time, so there is a demand for metal supports that are easy to handle and have excellent stability. The metal supports of the present invention are advantageous in this respect. EXAMPLES

[0106] The present invention will now be further described with reference to examples, although it is needless to say that the present invention is not limited to these examples.

[0107] <Measurement of ammonia synthesis activity> The ammonia synthesis activity of the metal carrier was measured using a fixed-bed flow-type reactor. The metal carrier, which had been pretreated by the method described in the Examples and Comparative Examples, was allowed to cool to 300°C while flowing Ar. While maintaining the temperature of the metal carrier layer at 300°C, the pressure was increased to 1.0 MPa or 3.0 MPa using the back pressure valve at the outlet of the reaction tube while supplying Ar. The inclusion of Ar was stopped, and while maintaining the pressure, H2 and N2 were each supplied at 90 mL min. -1 , 30mL min -1 (Space velocity 72L h -1 g -1 ) and transferred to the reaction atmosphere. 200mL of sulfuric acid aqueous solution of 1 to 100mM (1,5,10,25,100mM) depending on the level of NH3 synthesis activity was added to a three-necked flask connected to an electric conductivity meter, and a mixed gas containing hydrogen (purity, 99.995%, Fukuoka Oxygen), nitrogen (purity, 99.995%, Fukuoka Oxygen), and NH3 flowing out from the outlet of the reaction tube was bubbled into the sulfuric acid aqueous solution. In addition, to remove impurities such as moisture and oxygen, a gas purifier (gas purification filter MC50-904F, SAES) was used to set the purity to 99.99999999 or more. At this time, the amount of ammonia produced in the outlet gas was quantified by measuring the change in electric conductivity caused by the reaction of NH3 and sulfuric acid. Next, the temperature of the metal support layer was raised to 350°C, 400°C, or 450°C. After the temperature of the metal carrier layer was stabilized at 350° C., 400° C., or 450° C., it was left for 10 minutes, and the amount of ammonia produced was quantified in the same manner as above.

[0108] <Powder X-ray diffraction> Powder X-ray diffraction patterns of the metal supports (catalysts) were measured using a SmartLab x-ray diffractometer (Rigaku).

[0109] <Specific surface area (SSA) measurement> The specific surface area of ​​the metal support was determined by the BET method using a BEL-sorp mini (BEL Japan) from the amount of nitrogen adsorption at 77 K. Before the measurement, the sample was pretreated by vacuum heating at 300° C. for 2 hours.

[0110] 1. Co / Ba0.01 Mg 0.99 O x _Reduction at 700 °C and Co / Ba 0.05 La 0.95 O x _Comparison of reduction at 700 °C (Example 1) <Co / Ba 0.01 Mg 0.95 O x _Reduction at 700 °C > <Preparation of composite oxide> Ba 0.01 Mg 0.99 O x The composite oxide was synthesized as follows. Ba(OH)2 (Wako Pure Chemical Industries) was dissolved in purified water to obtain an aqueous Ba(OH)2 solution, and 200 mL of a precursor solution containing 0.000625 mol of Ba was prepared. 2.5 g of MgO (UBE Materials) was added thereto, and while stirring at 320 rpm with a magnetic stirrer, the stirring was continued at room temperature for 1 hour. After the suspension was evaporated to dryness using a rotary evaporator, the obtained powder was dried overnight using an oven set at 80 °C. The dried powder was pulverized in a mortar, and the obtained powder was heated at 700 °C for 5 hours in an electric furnace under an air atmosphere to obtain Ba 0.01 Mg 0.99 O x was obtained.

[0111] <Loading of Co Co was loaded onto the carrier Ba 0.01 Mg 0.99 O x by an impregnation method. A solution of cobalt(II) acetylacetonate (Wako Pure Chemical Industries), which is a Co precursor, dissolved in tetrahydrofuran (THF) (Wako Pure Chemical Industries) was prepared in a 200 mL eggplant flask, 1 g of the carrier was added thereto, and stirring was carried out at room temperature for 18 hours or more. The amount of cobalt(II) acetylacetonate and the carrier used was appropriately adjusted so that the amount of Co contained in the catalyst after heating under the following argon atmosphere would be 20% by weight. After the stirred suspension was dried under reduced pressure at 35 °C and 0.3 atm using a rotary evaporator, it was dried at 80 °C for 18 hours using an oven. The obtained powder was 80 mL min -1The precursor was heated at 500°C for 5 hours in a tubular electric furnace under a constant flow of argon to remove the acetylacetonato ligands. 0.01 Mg 0.99 O x Metal supports were obtained.

[0112] <Hydrogen reduction pretreatment> The Co / Ba ratio obtained above 0.01 Mg 0.99 O x The product was subjected to hydrogen reduction pretreatment (also simply referred to as "pretreatment") by the following method. The powder of the metal carrier was pressurized at 20 MPa for 5 minutes to produce a disk, which was then crushed in a mortar and classified with a sieve to produce pellets. The pellet size was adjusted to a diameter of 250 to 500 μm. 100 mg of the pellets were packed into an Inconel (trademark) catalytic reaction tube with a diameter of 7 mm, and the front and rear of the catalytic layer were fixed with quartz wool. This reaction tube was placed in a fixed-bed flow-type reaction apparatus for measuring ammonia synthesis activity, and 60 mL min was poured into the reaction tube filled with the pellets. -1 The mixture was heated at 700℃ for 1 hour under a 100% H2 atmosphere. 0.01 Mg 0.99 O x The reduction was achieved at 700℃.

[0113] Comparative Example 1 <Co / Ba 0.05 La 0.95 O x _700℃ reduction> Co / Ba of Example 101 of Patent Document 6 (International Publication No. 2019 / 216304) 0.05 La 0.95 O x The reduction at 700°C was used as a comparative example. 0.05 La 0.95 O x _700℃ reduction was produced.

[0114] Ammonia synthesis was carried out at various temperatures (300°C, 350°C, 400°C, 450°C) under a reaction pressure of 1 MPa for the metal-supported materials of Example 1 and Comparative Example 1, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0115] [Table 3]

[0116] The results are shown in Figure 1. The right side of the vertical axis in this figure shows the ammonia synthesis rate, the left side of the vertical axis shows the ammonia yield, and the horizontal axis shows the reaction temperature. This figure shows that at all reaction temperatures, the metal-supported material of Example 1 is superior in ammonia synthesis rate and yield to the metal-supported material of Comparative Example 1. It is also clear that the higher the reaction temperature for ammonia synthesis, the higher the ammonia synthesis activity (synthesis rate, yield).

[0117] 2. Study of Ba Addition Amount (Examples 1 to 6, Comparative Example 2) In Example 1, the ratio of the moles of Ba to the total moles of Ba and Mg was variously changed (0 mol% (Comparative Example 2), 0.5 mol% (Example 2), 1 mol% (Example 1), 2 mol% (Example 3), 3 mol% (Example 4), 5 mol% (Example 5), 10 mol% (Example 6)) to produce metal-supported materials.

[0118] Ammonia synthesis was carried out at various temperatures (300°C, 350°C, 400°C, 450°C) under a reaction pressure of 1 MPa for the metal-supported materials of Examples 1 to 6 and Comparative Example 2, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0119] [Table 4]

[0120] The results are shown in Figures 2 and 3. From these figures, it was found that the ammonia synthesis activity increases with increasing amount of Ba added, but the ammonia synthesis activity reaches its maximum at an amount of 1 mol%, and the ammonia synthesis activity gradually decreases when the amount of Ba added is increased beyond that. Also, from Figure 3, it is found that the amount of Ba added that provides high ammonia synthesis activity is within the range of 0.5 to 3 mol%.

[0121] 3. Study of reduction temperature (Examples 7 to 11) In Example 1, the amount of Co supported was set to 20 wt%, and the reduction temperature was changed in various ways (500°C (Example 7), 650°C (Example 8), 700°C (Example 9), 800°C (Example 10), and 900°C (Example 11)) to produce metal-supported materials.

[0122] For the metal-supported materials of Examples 7 to 11, ammonia synthesis was carried out at a reaction pressure of 1 MPa and various temperatures (300°C, 350°C, 400°C, 450°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0123] [Table 5]

[0124] The results are shown in Figures 4 and 5. It was found from these figures that the ammonia synthesis activity was relatively low when the reduction temperature was 500°C, but increased at temperatures of 650°C or higher.

[0125] FIG. 6 shows the XRD patterns of the metal-supported materials in Example 7 (reduction temperature 500°C), Example 9 (reduction temperature 700°C), and Example 10 (reduction temperature 800°C). In the figure, "fresh" is the sample before the reduction treatment. As can be seen from this figure, BaCO3 is decomposed by the reduction treatment, and when the reduction temperature is raised to about 700°C, the BaCO3 peak is no longer observed, so it is understood that BaCO3 is decomposed. It can also be seen that when the reduction temperature is raised to 800°C, a peak of metal Co that had not been observed until then is observed. This is thought to be because the Co particles that were somewhat dispersed aggregated due to the high-temperature reduction treatment, and the metal Co peak that was not observed because the Co particles were highly dispersed is observed.

[0126] The following table shows various parameters of the metal carrier at a reaction temperature of 350° C. in Example 7 (reduction temperature 500° C.), Example 9 (reduction temperature 700° C.), Example 10 (reduction temperature 800° C.), and Comparative Example 2 (no Ba, reduction temperature 700° C.). From this table, it can be seen that the specific surface area (SSA) decreases with increasing reduction temperature, but the ammonia synthesis activity improves.

[0127] [Table 6]

[0128] 4. Examination of Co-loading Amount (Example 12, Example 1, Example 15) In Example 1, the amount of Co supported was changed in various ways (5 wt% (Example 12), 10 wt% (Example 13), 20 wt% (Example 1), 30 wt% (Example 15)) to produce metal-supported materials.

[0129] Ammonia synthesis was carried out for the metal supports of Examples 12, 1, and 15 at various temperatures (300°C, 350°C, 400°C, and 450°C) at a reaction pressure of 1 MPa, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0130] [Table 7]

[0131] The results are shown in Figures 7 and 8. It was found from these figures that the ammonia synthesis activity increased as the Co loading increased, and reached a maximum at 20 wt%.

[0132] (Comparative Examples 1, 4, and 5) As a comparison example, Co / Ba 0.05 La 0.95 O x (Comparative Example 1), Ru / CeO x , (Comparative Example 4), Cs + / Ru / MgO x (Comparative Example 5) was prepared. Ru / CeOx , (Comparative Example 4) was prepared by the following method. Ru was supported on CeO2 by impregnation. Ru3(CO), which is a Ru precursor, was used. 12 A tetrahydrofuran (THF) (Wako Pure Chemical Industries) solution containing Ru3(CO) was prepared in a 200 mL eggplant flask, to which 5 g of CeO2 (Daiichi Kigenso Kagaku Kogyo) was added, and the mixture was stirred at room temperature for 18 hours or more. 12 The amount of the catalyst and the carrier were appropriately adjusted so that the amount of Ru contained in the catalyst after heating under an argon atmosphere would be 5 wt%. The stirred suspension was dried under reduced pressure at 35°C and 0.3 atm using a rotary evaporator, and then dried at 80°C for 18 hours in an oven. The obtained powder was then heated at 500°C for 5 hours at 80 mL min -1 The carbonyl ligands in the precursor were removed by heating in a tubular electric furnace under argon flow at 400°C. Ru / CeO2 was obtained by the above operations. The reduction treatment was carried out at 400°C.

[0133] Cs + / Ru / MgO x Comparative Example 5 was prepared by the method described in the non-patent literature (F. Rosowski, A. Hornung, O. Hinrichsen, D. Herein, M. Muhler and G. Ertl, Appl. Catal., A, 1997, 151, 443-460.). The amount of Ru supported was 5 wt%, and Cs / Ru was 1 / 1 (mol / mol). The reduction treatment was carried out at 500°C.

[0134] Ammonia synthesis was carried out at various temperatures (300°C, 350°C, 400°C, 450°C) and pressures (0.1MPa, 1.0MPa, 3.0MPa) for the metal-supported materials of Comparative Examples 3 to 5, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0135] [Table 8]

[0136] The results are shown in FIG. 10 (reaction temperature 350° C.) and FIG. 11 (reaction temperature 400° C.). Example 3 (Co / Ba 0.01 Mg 0.99 O x ) are also shown in the figure. From this figure, it can be seen that the metal-supported materials of the examples have higher ammonia synthesis activity than the metal-supported materials of Comparative Examples 1, 4, and 5.

[0137] 6. Effects of pretreatment conditions (reducing conditions) (Example 1, Example 17, Comparative Example 6) In Example 1, the temperature and time of the hydrogen reduction pretreatment were changed to 500°C and 72 hours to prepare a metal support (Example 17). As a comparative example, 5wt%Ru / MgO (Comparative Example 6) was prepared in the same manner as in Comparative Example 4, except that the support was MgO (Ube Materials).

[0138] Ammonia synthesis was carried out for the metal-supported materials of Example 1, Example 17, and Comparative Example 6 at a reaction pressure of 1 MPa and various temperatures (300°C, 350°C, 400°C, 450°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0139] [Table 9]

[0140] The results are shown in Figure 12. It is clear from this figure that even under low pressure conditions, ammonia synthesis activity improves with prolonged reduction.

[0141] 7. Effect of Co precursor (Example 1, Example 18) A metal support was prepared in the same manner as in Example 1, except that Co(NO3)2·6H2O (Wako Pure Chemical Industries, Ltd.) was used instead of the Co precursor Co acetylacetonate(II) (Co(acac)), purified water was used instead of THF, and the atmosphere during firing was air.

[0142] For the metal supports of Example 1 and Example 18, ammonia synthesis was carried out at a reaction pressure of 1 MPa and various temperatures (300°C, 350°C, 400°C, 450°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0143] [Table 10]

[0144] The results are shown in Figure 13. This figure shows that the ammonia synthesis activity is improved when the Co precursor is Co(acac) rather than Co nitrate.

[0145] Figure 14 shows XRD of the metal-supported materials in Example 1 (Co(acac)) and Example 17 (Co nitrate). As can be seen from this figure, no peak derived from metallic Co was observed in the metal-supported material using Co(acac) as a precursor, but a peak derived from metallic Co was observed in the metal-supported material using nitric acid as a precursor. From this, it is presumed that Co is more highly dispersed in the metal-supported material using Co(acac) as a precursor than in the metal-supported material using Co nitrate as a precursor, resulting in improved ammonia synthesis activity.

[0146] 8.SV Study (Example 1) In Example 1, Co(NO3)2·6H2O (Wako Pure Chemical Industries, Ltd.) was used in place of the Co precursor Co acetylacetonate(II) (Co(acac)), to prepare a metal-supported material (Example 18).

[0147] For the metal-supported material of Example 1, the reaction pressure was 1 MPa, various temperatures (300°C, 350°C, 400°C, 450°C) and various SV (18 L / h -1 g -1 , 36L / h -1 g -1 , 72L / h -1 g -1 The ammonia synthesis activity was measured using the method described above. The results are shown in the table below.

[0148] [Table 11]

[0149] The results are shown in Figures 15 and 16. It was found from these figures that as the SV value increases, the ammonia synthesis rate increases (Figure 15), but the ammonia yield decreases (Figure 16).

[0150] 9. Study of Carrier Characteristics (Example 1, Comparative Example 7, Comparative Example 1) (5wt%Ru / Ba 0.1 La 0.45 Ce 0.45 Ox: Comparative example 7) In Comparative Example 1, Ba was used instead of CeO2. 0.1 La 0.45 Ce 0.45 The Ru content was adjusted appropriately to 5wt%Ru / Ba 0.1 La 0.45 Ce 0.45Ox (Comparative Example 7) was prepared. The carrier was synthesized by the reverse homogeneous precipitation method according to the method described in Example 6 of Patent Document 6 (International Publication No. 2019 / 216304) as follows. La(NO3)3·6H2O (Wako Pure Chemical Industries) was dissolved in purified water to prepare a La(NO3)3 aqueous solution. Ce(NO3)3·6H2O (Kanto Chemical) was dissolved in purified water to prepare a Ce(NO3)3 aqueous solution. Ba(NO3)2·6H2O (Wako Pure Chemical Industries) was dissolved in purified water to prepare a Ba(NO3)2 aqueous solution. The La(NO3)3 aqueous solution, the Ce(NO3)3 aqueous solution, and the Ba(NO3)2 aqueous solution were mixed to prepare 250 mL of a carrier precursor solution containing a total of 0.0625 mol of La, Ce, and Ba. 250 mL of 28% NH3 aqueous solution (Wako Pure Chemical Industries) was added to a 1000 mL beaker, and while stirring with a magnetic stirrer at 320 rpm, the above carrier precursor solution was added all at once and stirred for 1 hour. After that, it was left to stand for 12 hours, and precipitate (1) was separated by suction filtration. The separated filtrate was collected in a 2 L beaker. 350 mL of ion-exchanged water was added to the separated precipitate (1), and the precipitate was washed by stirring for 30 minutes, and precipitate (1) was separated by suction filtration. This washing operation was repeated three times. All the ion-exchanged water used for washing was collected, and the filtrate and washing solution were added to a 2 L beaker and mixed. This mixed solution was left to stand for 12 hours to generate a white precipitate (2), which was collected by suction filtration. Precipitate (1) and precipitate (2) were mixed and dried in an oven at 80 °C for 15 hours. The dried precipitate was crushed in a mortar, and the resulting powder was heated in an electric furnace at 700°C for 5 h in air to obtain Ba. 0.1 La 0.45 Ce 0.45 O x obtained.

[0151] Ammonia synthesis was carried out at a reaction pressure of 1 MPa and a reaction temperature of 350° C. for the metal-supported materials of Example 1, Comparative Example 1, and Comparative Example 7, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0152] [Table 12]

[0153] From this table, the 20 wt% Co / Ba in Example 1 0.01 Mg 0.99 Ox has a large specific surface area (SSA), which is presumed to contribute to improved ammonia synthesis activity.

[0154] 10. Activity at low temperatures (Example 1, Comparative Example 9, Comparative Example 10) As a comparison example, Ru / Ba 0.1 La 0.45 Ce 0.45 O x (700°C, 1h, red) (Comparative Example 9) was produced by the method described in Example 6 of Patent Document 6 (WO 2019 / 216304). Also, Ru / La 0.5 Ce 0.5 O x (650°C, 1h, red) (Comparative Example 10) was produced by the method described in Example 1 of Patent Document 6 (WO 2019 / 216304).

[0155] For Example 1, ammonia synthesis was performed at various temperatures (150°C, 200°C, 250°C) and various pressures (0.1MPa, 1.0MPa, 3.0MPa), and the ammonia synthesis activity was measured by the method described above. For the metal supports of Comparative Examples 9 and 10, ammonia synthesis (pressure 1.0MPa) was performed at various temperatures (150°C, 200°C, 250°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0156] [Table 13]

[0157] The results are shown in Figures 17 and 18. Figure 17 shows that the Co-supported catalyst exhibits higher activity than the Ru-supported catalyst at low temperature. Figure 18 shows that the ammonia synthesis activity improves with increasing pressure even at low temperature.

[0158] 11. Study of Ru-supported catalysts (Example 21, Comparative Examples 11 to 14) Example 21 <Ru / Ba 0.01 Mg 0.99 O x _700℃ reduction> In Example 1, Co acetylacetonate(II) was reacted with the Ru precursor Ru(CO) 12 The same procedure as in Example 1 was carried out except that Ru / Ba 0.05 Mg 0.95 O x The reduction was achieved at 700℃.

[0159] 11. Study of Fe-supported catalysts (Example 22, Comparative Example 15, Comparative Example 16) Example 22 <Fe / Ba 0.01 Mg 0.99 O x _700℃ reduction> The same procedure as in Example 1 was carried out, except that Co acetylacetonate (II) was replaced with Fe precursor iron (III) acetylacetonate (Dojindo Laboratories), to obtain Fe / Ba 0.01 Mg 0.99 O x The reduction was achieved at 700℃.

[0160] (Comparative Example 15 and Comparative Example 16) As a comparative example, a 20wt% Fe / Ba alloy was prepared in the same manner as in Comparative Example 9, except that Ru was replaced with Fe and the amount of Ba was changed. 0.1 La 0.45 CEO x (700° C., reduced for 1 hour) (Comparative Example 15) was prepared. Also, 5 wt % Ru / MgO (Comparative Example 16) was prepared in the same manner as in Comparative Example 6.

[0161] Ammonia synthesis was carried out for the metal-supported materials of Example 22, Comparative Example 15, and Comparative Example 16 at various temperatures (300°C, 350°C, 400°C, 450°C) under a reaction pressure of 1 MPa, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0162] [Table 14]

[0163] The results are shown in Figure 20. From this figure, it can be seen that the Fe-loaded metal supports are 5wt%Ru / MgO and 20wt%Fe / Ba 0.1 La 0.45 CEO x It was found that the ammonia synthesis activity was higher than that of the catalyst (700°C, 1 hour reduction).

[0164] 12. Study of pretreatment conditions: Fe-supported catalyst (Example 23, Example 24, Comparative Example 16) In Example 22, the pretreatment conditions were variously changed (H2+N2, 500°C, reduction for 72 hours (Example 23), H2 only, 700°C, reduction for 1 hour (Example 24)) to produce metal-supported materials.

[0165] Ammonia synthesis was carried out for the metal-supported materials of Example 23, Example 24, and Comparative Example 16 at a reaction pressure of 1 MPa and various temperatures (300°C, 350°C, 400°C, 450°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0166] [Table 15]

[0167] The results are shown in Figure 21. This figure shows that ammonia synthesis activity can be greatly improved depending on the pretreatment conditions.

[0168] 13. Study of Co-Fe catalyst (Examples 25 to 27) Example 7 (20wt% Co / Ba 0.05 Mg 0.95 O x ) The Fe precursor of Example 22 was added to the Co precursor to adjust the mixing ratio, thereby producing a metal-supported material (Example 25).

[0169] Ammonia synthesis was carried out at various temperatures (300°C, 350°C, 400°C, 450°C) for the metal supports of Examples 7, 22, and 25, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0170] [Table 16]

[0171] The results are shown in Figure 22. This figure shows that Co alone has a higher ammonia synthesis activity than Fe alone or the Fe-Co mixed catalyst.

[0172] 14. H2-TPR Measurement Results (Example 1, Comparative Example 2) Example 1 (Co / Ba 0.05 Mg 0.95 O x _700℃ reduction), Comparative Example 2 (Co / MgO x ) was subjected to H-Temperature Programmed Reduction (H2-TPR) measurements. H2-TPR is a method of continuously raising the temperature of a solid at a constant rate under a flow of hydrogen gas (H2) diluted with an inert gas such as argon, and measuring the consumption rate of hydrogen gas and the production rate of reaction products, using a mass spectrometer as a detector. The results are shown in Figures 23 and 24.

[0173] As shown in FIG. 23, the Co / BaMgO x It can be seen that the Co / MgO of Comparative Example 2 absorbs hydrogen with a molecular weight of 2 and releases methane with a molecular weight of 16 at a temperature of just over 500°C. It can also be seen that the Co / MgO of Comparative Example 2 releases water with a molecular weight of 18 at a temperature of just over 600°C. x From these, it can be seen that in Example 1, the reduction reaction of Ba according to the following formula (5) occurs. BaCO3+ 4H2→ BaO +CH4+ 2H2O (5)

[0174] These results suggest that BaCO3 and Ba(OH)2 are formed on the surface of the Co / BaMgOx catalyst, but that by heat treatment under hydrogen, H2 and BaCO3 react and decompose into Ba(OH)2 and CH4 at just over 500°C, and Ba(OH)2 decomposes into BaO and H2O at just over 600°C. In other words, by performing heat treatment under hydrogen, the BaCO3 and Ba(OH)2 that were formed on the surface become BaO, which is thought to improve catalytic activity.

[0175] FIG. 25 is an electron microscope photograph of the catalyst of Example 1. (1) is a HAADF-STEM image. From the element mapping images (2) to (5), the following can be inferred. In (1), the part that shines the whitest is Co, and the part that shines the next light gray is the part where magnesium oxide is present. Looking at (5), it can be seen that the barium oxide particles are even smaller than the Co particles and are uniformly distributed on the Co / MgO. The barium oxide particles are at most about 10% of the particle size of the Co particles. The order of preparation of the catalyst is such that barium hydroxide is supported on the magnesium oxide carrier, and then cobalt is supported on top of that. Therefore, it is considered that the barium oxide particles move onto the cobalt particles under the catalyst preparation conditions, and that the barium compound was already uniformly distributed on the surface of the magnesium oxide before the cobalt was supported, so that Ba is also present near the interface between the magnesium oxide and cobalt. The overlapping image (5) shows that Ba surrounds Co, forming a nano-order core (Co particles) / shell (barium oxide) structure. In this catalyst, the surface cobalt atoms close to the barium oxide receive strong electrical donors, resulting in high ammonia synthesis activity. This supports the above consideration.

[0176] FIG. 34 is an electron microscope photograph of the catalyst of Example 17. (1) is an HAADF-STEM image. (2) to (5) are element mapping images, and the following can be considered by comparing with FIG. 25. In the case of reduction at 500°C for 72 hours (FIG. 34), the reduction temperature is lower than that of reduction at 700°C for 1 hour (FIG. 25), so that a nano-order core (Co particle) / shell (barium oxide) structure is observed, but the particle diameter of barium oxide is small and the mobility of barium oxide on the cobalt particles is somewhat low. However, since the reduction treatment was performed for a long time, it is considered that the decomposition of barium carbonate and hydroxide is more advanced than in the case of reduction at 500°C for 1 hour (Example 7). On the other hand, since the reduction temperature is low, the cobalt particle diameter is small, and since the reduction treatment was performed for a long time, the reduction degree of cobalt is higher than that of reduction at 500°C for 1 hour (Example 7), and the number of surface cobalt atoms in a metallic state that contribute to ammonia synthesis is increased. Therefore, the catalyst of Example 17 exhibits ammonia synthesis activity comparable to that of the catalyst of Example 1.

[0177] As in Examples 33 and 34 described below, in the case of double addition of a Group 1 element and a Group 2 element, ammonia synthesis activity was further improved compared to Example 17. This is because the Group 1 element, which is a stronger basic element than the oxide of the Group 2 element, was incorporated into the shell structure of barium oxide, and the surface cobalt atoms close to the shell received very strong electrical donation.

[0178] 15. Ammonia synthesis activity of catalysts in which Ba was replaced with other group II elements (Sr, Ca) (Examples 26 to 27) In Example 1, Sr(OH)2 and Ca(OH)2 were used instead of the raw material Ba(OH)2, and 20 wt% Co / Sr 0.01 Mg 0.99 O x (Example 26) and 20wt% Co / Ca 0.01 Mg 0.99 O x(Example 27) was prepared. Ammonia synthesis was carried out on these metal supports at various temperatures (300°C, 350°C, 400°C, 450°C) and the ammonia synthesis activity was measured by the method described above. The ammonia synthesis conditions were reaction pressure of 1.0 MPa, reaction gas H2 / N2=90 / 30 cc / min (total flow rate 120 cc / min), and working temperature of 0.1 g (SV=72 L h -1 g -1 The results are shown in the table below.

[0179] [Table 17]

[0180] The results are shown in Figure 26. From this figure, it can be seen that Group 2 elements other than Ba ​​(Sr, Ca) also had higher activity than MgO alone, and the effect of improving ammonia synthesis activity by their addition was confirmed.

[0181] 16. Addition of Group 1 elements instead of Group 2 elements (Examples 28 to 31) In Example 1, KNO3, KOH, LiNO3, and LiOH were used instead of the raw material Ba(OH)2 to produce composite oxides at various reduction temperatures. 0.03 Mg 0.97 O x (Example 28), 20wt% Co / K 0.03 Mg 0.97 O x (Example 29), 20wt% Co / Li 0.03 Mg 0.97 O x (Example 30), 20wt% Co / Li 0.03 Mg 0.97 O x (Example 31) was prepared. Ammonia synthesis was carried out on these metal supports at various temperatures (300°C, 350°C, 400°C, 450°C), and the ammonia synthesis activity was measured by the method described above. The results are shown in Figure 27. From this figure, it was found that the system in which K was added using KOH showed some effect of improving ammonia activity, but the ammonia synthesis activity was not as remarkably high as that of the Group 2 elements.

[0182] 17. Double addition of Group 1 element + Group 2 element (Examples 32 to 34) In Example 1, composite oxides were produced using CsOH, RbOH, and KOH in addition to the raw material Ba(OH)2, and pre-treated under reduction conditions at 700°C for 1 hour. 0.01 Ba 0.01 Mg 0.98 O x _700℃, 1h reduction (Example 32), 20wt%Co / Rb 0.01 Ba 0.01 Mg 0.98 O x _700℃, 1h reduction (Example 33), 20wt%Co / K 0.01 Ba 0.01 Mg 0.98 O x 700℃, 1h reduction (Example 34) was prepared. Ammonia synthesis was carried out on these metal supports at various temperatures (300℃, 350℃, 400℃, 450℃), and the ammonia synthesis activity was measured by the above-mentioned method. The results are shown in the table below.

[0183] [Table 18]

[0184] The results are shown in Figure 28. From this figure, when 1 mol% of a Group 1 element was added and the pretreatment conditions were fixed at 700°C and 1 hour, the activity was slightly lower than when no Group 1 element was added (Ba only), but the ammonia synthesis activity was about the same as when only Ba was added. However, since the ammonia synthesis activity was the highest when only Ba was added, no improvement in ammonia synthesis activity was observed by adding a Group 1 element (double addition).

[0185] 18. Double addition of Group 1 element + Group 2 element (study of reduction conditions 1) (Examples 35 to 36) In Example 30, the amount of KOH in the raw material was increased and the reduction conditions were changed to 20 wt% Co / K 0.03 Ba 0.01 Mg0.96 O x _500℃, 72h reduction (Example 35), 20wt%Co / K 0.03 Ba 0.01 Mg 0.96 O x 700℃, 1h reduction (Example 36) was prepared. Ammonia synthesis was carried out on these metal-supported materials at various temperatures (300℃, 350℃, 400℃, 450℃), and the ammonia synthesis activity was measured by the above-mentioned method. The results are shown in the table below.

[0186] [Table 19]

[0187] The results are shown in Figure 29. From this figure, in the case of 3 mol% K + 1 mol% Ba, no effect on improving ammonia synthesis activity was observed even when reduction was performed for a long period of time at a low temperature.

[0188] 19. Double addition of Group 1 element + Group 2 element (Study of reduction conditions 2) (Example 37) In Example 30, the amount of KOH in the raw material was not changed, and the reduction conditions were changed to 20 wt% Co / K 0.01 Ba 0.01 Mg 0.98 O x 500℃, 72h reduction (Example 37) was prepared. Ammonia synthesis was carried out on these metal-supported materials at various temperatures (300℃, 350℃, 400℃, 450℃), and the ammonia synthesis activity was measured by the above-mentioned method. The results are shown in the table below.

[0189] [Table 20]

[0190] The results are shown in Figure 30. From this figure, it was found that in the case of 1 mol% K + 1 mol% Ba, activity improves when reduced for a long time at a low temperature. In addition, the figure shows that the effect of equilibrium appears around the reaction temperature of 450°C, and it is presumed that the ammonia synthesis activity is about the same in both cases.

[0191] 20. Double addition of Group 1 element + Group 2 element (Study of reduction conditions 3) (Example 38) In Example 29, the reduction conditions were changed to 20 wt% Co / Rb 0.01 Ba 0.01 Mg 0.98 O x 500℃, 72h reduction (Example 38) was prepared. Ammonia synthesis was carried out on these metal-supported materials at various temperatures (300℃, 350℃, 400℃, 450℃), and the ammonia synthesis activity was measured by the above-mentioned method. The results are shown in the table below.

[0192] [Table 21]

[0193] The results are shown in Figure 31. From this figure, it was found that in the case of 1 mol% Rb + 1 mol% Ba, activity improves when reduced for a long time at a low temperature. In addition, the figure shows that the effect of equilibrium appears around the reaction temperature of 450°C, and it is presumed that the ammonia synthesis activity is about the same in both cases.

[0194] 21. Ni instead of Co (Reaction Pressure Study 1) (Example 39) The same procedure as in Example 1 was carried out except that Co acetylacetonate (II) was replaced with Ni precursor acetylacetonate nickel (II) (Kishida Chemical Co., Ltd.), and Ni / Ba 0.01 Mg 0.99 O x The metal-supported material was reduced at 700°C for 1 hour (Example 35). Ammonia synthesis was carried out at 1.0 MPa and various temperatures (300°C, 350°C, 400°C, 450°C) for this metal-supported material (Example 39) and the metal-supported materials of Examples 1 and 22, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0195] [Table 22]

[0196] The results are shown in Figure 32. This figure shows that the Ni-supported catalyst has higher ammonia synthesis activity than the Fe-supported catalyst at 450°C.

[0197] 22. Ni instead of Co (Reaction Pressure Study 2) (Example 40) Ammonia synthesis was carried out under the condition of 3.0 MPa for the metal-supported materials of Example 1, Example 22 and Example 40, and the ammonia synthesis activity was measured by the method described above. The results are shown in the table below.

[0198] [Table 23]

[0199] The results are shown in Figure 33. From this figure, it can be seen that both the Ni-supported catalyst and the Fe-supported catalyst each exhibited relatively high activity even at 3 MPa. However, the Ni-supported catalyst appears to be slightly affected by poisoning.

[0200] 23. Co reduction degree To compare the effect of hydrogen reduction on the reduction state of Co in the catalyst, we measured the X-ray absorption near edge structure (XANES) spectrum at the Co K absorption edge of Co / BaMgOx. The catalyst before reduction and the standard sample for comparison were prepared as samples for XANES spectrum measurement by the following method. The catalyst before reduction and the standard sample were mixed with boron nitride powder by grinding in air, and the mixed powder was pressed into a disk shape with a diameter of 10 mm. At this time, the ratio of boron nitride to each catalyst and standard sample and the thickness of the disk were appropriately adjusted so that the concentration of Co in the measurement target was optimized for the absorbance of the X-rays transmitted during the spectrum measurement.

[0201] The catalyst after reduction was prepared as a sample for XANES spectrum measurement by the following method. The catalyst was filled into a sample tube and connected to a fixed-bed flow-type reactor, and reduced by heating at a specified temperature for 1 hour while flowing hydrogen. The catalyst after reduction was cooled to room temperature while supplying inert gas (Ar) to the sample tube. The sample tube of this reactor has a cock on the gas inlet and outlet side, and by closing these cocks after cooling, the catalyst can be kept without contacting the atmosphere even when removed from the reactor. The reduced catalyst was transferred to a glove box filled with inert gas using this sample tube, and the reduced catalyst and boron nitride powder were ground and mixed in the glove box, and the mixed powder was pressure-molded into a disk with a diameter of 10 mm. At this time, the ratio of each catalyst to boron nitride and the thickness of the disk were appropriately adjusted so that the concentration of Co in the measurement target was optimized for the absorbance of X-rays transmitted during spectrum measurement.

[0202] The molded disk was triple-encapsulated in an oxygen-blocking resin bag in a glove box. This allows the spectrum to be measured without the catalyst being affected by reoxidation by oxygen even if the resin bag is taken out of the glove box into the atmosphere.

[0203] The XANES spectra of each sample were measured at BL01B1 of the large synchrotron radiation facility (SPirng-8). An ion chamber was used as a detector, and the spectra measured by the transmission method were analyzed using X-ray absorption spectrum analysis software (Athena, Demeter 0.9.26).

[0204] Figure 36 shows the normalized XANES spectra of the catalyst and standard sample. Comparing the spectral shape of the unreduced catalyst with that of the standard sample, the energy position and shape of the XANES spectrum of the unreduced catalyst, both with and without Ba, were found to be in good agreement with those of oxide (II) (CoO). This suggests that Co exists as CoO in the unreduced catalyst. Furthermore, by carrying out the reduction treatment, the shape of the XANES spectrum became closer to that of Co foil. This means that the Co in the catalyst was converted to a metallic state by the reduction treatment.

[0205] Therefore, the normalized XANES spectrum of each catalyst after reduction treatment was fitted with a linear combination fitting based on the spectra of standard samples of metallic Co foil and Co oxide (II) to estimate the proportion of metallic Co contained in the catalyst (degree of reduction). As a result, the Co / BaMgOx catalyst was After 1 hour of reduction at 500℃, the degree of reduction of Co was 71%. After reduction at 700° C. for 1 hour (catalyst of Example 1), the degree of Co reduction was 93%. It was found that as the reduction temperature increased, the proportion of Co oxides, which are inactive for ammonia synthesis, decreased, while the proportion of metallic Co, which is active for ammonia synthesis, increased.

Claims

1. A metal-supported material in which metal particles M are supported on a composite oxide composed of an oxide of a metal element L and an oxide of a metal element N, (A) The composite oxide is represented by the composition of the following general formula (1) and is the following (a) to (d): L ｎ N １－ｎ (1) (a) the metal element L is selected from the group consisting of Ba and Sr; (b) the metal element N is selected from the group consisting of Mg and Be; (c) n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the oxide particles of the metal element L are deposited on the surfaces of the oxide particles of the metal element N; (B) the metal particles M are one or more selected from the group consisting of Fe, Co, and Ni, (C) A metal-supported material in which the metal particles M are supported on an oxide of a metal element L deposited on the surface of an oxide of a metal element N, and oxide particles of the metal element L are deposited on the surfaces of the metal particles M.

2. (a) The metal element L is a partial negative charge (−δ ＯＡ ) is a strongly basic metal element having a value of 0.56 to 0.70, (b) The metal element N is a partial negative charge (−δ ＯＢ 2. The metal-supported material according to claim 1, characterized in that the metal element is a weakly basic element having a value of 0.35 or more and 0.55 or less.

3. The metal support according to claim 1, characterized in that the composite oxide is a binary composite oxide consisting of a metal element A contained in a metal element L and a metal element B contained in a metal element N, and the general formula (1) is represented by the composition of the following general formula (2), and is the following (a) to (d): A ｎ B １－ｎ (2) (a) The metal element A is a partial negative charge (−δ ＯＡ ) is 0.56 or more and 0.70 or less, which is a strongly basic element of Group 2 element, (b) The metal element B is a partial negative charge (−δ ＯＢ ) is 0.35 or more and 0.55 or less, (c) n is equal to or greater than 0.001 and equal to or less than 0.300; (d) The oxide of the metal element A and the oxide of the metal element B do not form a solid solution, and the oxide particles of the metal element A are deposited on the surfaces of the oxide particles of the metal element B.

4. A metal-supported material in which metal particles M are supported on a composite oxide composed of an oxide of a metal element L and an oxide of a metal element N, (A) The composite oxide is represented by the composition of the following general formula (3) and is the following (a) to (d): L ｎ N １－ｎ O ｘ (3) (a) the metal element L is selected from the group consisting of Ba and Sr; (b) the metal element N is selected from the group consisting of Mg and Be; (c) n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element L and the oxide of the metal element N do not form a solid solution, and the oxide particles of the metal element L are deposited on the surfaces of the oxide particles of the metal element N; (B) the metal particles M are one or more selected from the group consisting of Fe, Co, and Ni, (C) A metal-supported material in which the metal particles M are supported on an oxide of a metal element L deposited on the surface of an oxide of a metal element N, and oxide particles of the metal element L are deposited on the surfaces of the metal particles M.

5. (a) The metal element L is a partial negative charge (−δ ＯＡ ) is a strongly basic metal element having a value of 0.56 to 0.70, (b) The metal element N is a partial negative charge (−δ ＯＢ 5. The metal-supported material according to claim 4, characterized in that the metal element is a weakly basic element having a value of 0.35 or more and 0.55 or less.

6. The metal support according to claim 4, characterized in that the composite oxide is a binary composite oxide consisting of a metal element A contained in a metal element L and a metal element B contained in a metal element N, and the general formula (3) is represented by the composition of the following general formula (4), and is the following (a) to (d): A ｎ B １－ｎ O ｘ (4) (a) The metal element A is a partial negative charge (−δ ＯＡ ) is 0.56 or more and 0.70 or less, which is a strongly basic element of Group 2 element, (b) The metal element B is a partial negative charge (−δ ＯＢ ) is 0.35 or more and 0.55 or less, (c) n is equal to or greater than 0.001 and equal to or less than 0.300; (d) the oxide of the metal element A and the oxide of the metal element B do not form a solid solution, and the oxide particles of the metal element A are deposited on the surfaces of the oxide particles of the metal element B; (e) A metal-supporting material, wherein the x is the number of oxygen atoms required for the composite oxide to maintain electrical neutrality.

7. The composite oxide is Ba ｎ Mg １－ｎ O ｘ 5. The metal-supported material according to claim 1, wherein n is 0.001≦n≦0.

300.

8. The composite oxide is Ba ｎ Mg １－ｎ O ｘ 8. The metal support according to claim 7, characterized in that n satisfies the condition 0.01≦n≦0.

10.

9. 8. The metal support according to claim 7, wherein the amount of carbonate contained in the composite oxide is 10 mol % or less relative to Ba.

10. 2. The metal support according to claim 1, wherein oxide particles of the metal element N are distributed between the oxide particles of the metal element L and the metal particles M.

11. 2. The metal support according to claim 1, wherein the metal particles M are cobalt particles.

12. A catalyst for ammonia synthesis, comprising the metal carrier according to claim 1.

13. The method for producing a metal-supported material according to claim 1, comprising the following steps (a) to (d): (a) an immersion step of impregnating an N precursor containing the metal element N with an L precursor containing the metal element L to obtain a mixture; (b) a composite oxide calcination step of calcining the mixture at a temperature of 500° C. or higher to obtain a support made of a composite oxide; (c) a supporting step of impregnating the composite oxide with a precursor of a compound containing the metal particles M to obtain an impregnated support; (d) a support calcination step of calcining the impregnated support at a temperature of 400° C. or higher; (e) A reduction step of calcining the metal-supported material obtained in (d) at 500° C. or higher in the presence of hydrogen.

14. 13. A method for producing ammonia by contacting hydrogen and nitrogen with a catalyst, wherein the catalyst is the ammonia synthesis catalyst according to claim 12.

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