Composite oxide, metal support, and ammonia synthesis catalyst

Abstract

The composite oxide of the present application contains metal elements represented by the composition of general formula (1): A n X y M m (1), in which general formula (1), A is a lanthanoid element characterized by at least a part or all of it being in a state of III valence; X is a Group 2 element of the periodic table selected from the group consisting of Ca, Sr, and Ba, or is a lanthanoid element, and represents an element different from A; M is any one of a Group 1 element of the periodic table and a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A and X; n satisfies 0

Description

TECHNICAL FIELD

[0001] The present application relates to a composite oxide which can be used for synthesizing ammonia under mild conditions, a metal support using the composite oxide and an ammonia synthesis catalyst, and a method for producing the composite oxide, a method for producing the metal support and a method for producing ammonia. BACKGROUND

[0002] Ammonia is an important raw material in the modern chemical industry. More than 80% of the ammonia produced is used as a chemical fertilizer for agricultural crops. In addition, ammonia is also attracting attention as a carrier of energy and hydrogen. This is because: (1) it has a high hydrogen content (17.6 wt%), (2) it has a high energy density (12.8 GJ / m 3 ), and (3) it does not produce carbon dioxide when decomposed to produce hydrogen. If ammonia can be efficiently produced from renewable energy sources such as solar and wind energy, it can alleviate the earth-scale problems associated with energy and food crises.

[0003] Currently, the Haber-Bosch method for producing ammonia consumes a large amount of energy, which accounts for about 1 to 2% of the world's energy consumption. About 60% of the consumed energy is recovered by this method, which ensures the enthalpy of ammonia. However, most of the remaining energy is lost when hydrogen is produced from natural gas, ammonia synthesis, and gas separation. Since the Haber-Bosch method for ammonia synthesis is carried out at very high temperatures (> 450°C) and pressures (> 20 MPa), there is an urgent need to reduce the large amount of energy used in this method. In order to suppress the earth-scale energy consumption, a catalyst that can synthesize ammonia under more mild conditions (lower temperature and pressure) compared to the iron-based catalyst used in the Haber-Bosch method is needed.

[0004] In recent years, a method for producing ammonia at low pressure conditions of about 1 MPa (10 atm) has been known. The ruthenium catalyst used to produce ammonia is usually supported on a support. For example, it is disclosed in Patent Literature 1 that if a rare earth oxide is used as a support for ruthenium, the amount of ruthenium used can be reduced, and the reaction temperature can be reduced. However, in the ammonia production method of Patent Literature 1, the ammonia yield is not sufficient when ammonia is produced at low pressure conditions.

[0005] In addition to Patent Literature 1, in various patent literatures, there are disclosed ammonia synthesis catalysts in which ruthenium is supported on various kinds of rare earth oxide supports. As representatives, there can be cited Patent Literatures 2 to 4, Non-Patent Literature 1. In Patent Literature 2 and Patent Literature 4, lanthanoid oxide is disclosed as the support, in Patent Literature 3, praseodymium oxide is disclosed as the support, and in Non-Patent Literature 1, Ce oxide is disclosed as the support. In Non-Patent Literature 2, there is disclosed a Ru / CeO2-La2O3-based catalyst manufactured by co-precipitating, drying, and activating hydroxides of Ru, Ce, and La.

[0006] In the prior art literatures including Patent Literatures 1, 2, 4, Non-Patent Literature 1, it is described that, in the ruthenium catalyst used for synthesis of ammonia, Ru exists in the form of particles on the surface of the support. In the case of existing in the form of particles, there is a report that the average diameter thereof is greater than 5 nm (cf. Non-Patent Literature 2). In addition, in Patent Literature 3, it is disclosed that Ru is in the form of eggshell structure.

[0007] Synthesis catalysts generally require high synthesis activity. For the ruthenium catalyst for ammonia synthesis that is being developed, there has been a demand for a highly active catalyst that enables higher yield.

[0008] In addition, the catalyst needs to be replaced periodically when used in a synthesis reactor, and thus needs to be easy to handle. With respect to the ruthenium catalyst for ammonia synthesis, there has also been a demand for improvement in handling easiness.

[0009] Prior Art Literature

[0010] Patent Literature

[0011] Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 6-079177

[0012] Patent Literature 2: Japanese Patent Application Laid-Open (JP-A) No. 2013-111562

[0013] Patent Literature 3: International Publication No. 2016 / 133213

[0014] Patent Literature 4: Japanese Patent Application Laid-Open (JP-A) No. 2017-018907

[0015] Non-Patent Literature

[0016] Non-Patent Literature 1: Y. Niwa and K. Aika, Chemistry Letters, (1996) 3-4

[0017] Non-Patent Literature 2: X. Luo et al. Catalysis Letters 133, 382 (2009) SUMMARY

[0018] Technical problem to be solved by the invention

[0019] The present invention solves the above-described technical problem, and aims to provide a composite oxide capable of supporting a metal catalyst such as ruthenium and further improving ammonia synthesis activity. In addition, another object of the present invention is to provide a metal support supporting a metal catalyst such as ruthenium and further improving ammonia synthesis activity and a catalyst for ammonia synthesis. Furthermore, still another object of the present invention is to provide a method for producing a composite oxide capable of improving ammonia synthesis activity, a method for producing a metal support capable of improving ammonia synthesis activity, and a method for producing ammonia.

[0020] Method for solving the technical problem

[0021] The present inventors have found that, in a metal support using a composite oxide as a carrier, a metal oxide constituting the composite oxide shows good catalyst activity when it is in a specific valence state, and that partial negative charge of oxygen of the composite oxide affects catalyst activity, in order to solve the above-described technical problem, and have completed the following invention.

[0022] Note that the "composite oxide" of the present invention refers to, in a narrow sense, an oxide of a plurality of elements having a uniform phase, i.e., so-called solid solution, but in a broad sense, also includes a case where an oxide of a plurality of elements shows a non-uniform phase and a case where a composition of an oxide of a plurality of elements.

[0023] (1) A composite oxide comprising metal elements represented by a composition of general formula (1):

[0024] A n X y M m (1),

[0025] (in the general formula (1),

[0026] A is a lanthanoid element characterized by at least a part or all being in a state of III valence,

[0027] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from the A,

[0028] M is any one of a Group 1 element of the periodic table and a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from the A and the X,

[0029] n satisfies 0 < n < 1,

[0030] y satisfies 0 < y < 1,

[0031] m satisfies 0 ≤ m < 1,

[0032] and n + y + m = 1.

[0033] 〔1A〕 A composite oxide containing metal elements represented by a composition of general formula (1A) and having a partial negative charge of oxygen of 0.52 or more as defined by formula (A):

[0034] A n X y M m (1A)

[0035] ((Πχi ni ) 1 / Σni -5.21) / -4.75··(A)

[0036] (In the general formula (1A), A is a lanthanoid element characterized by being at least a part or all in a state of III valence; X is a Group 2 element of the periodic table selected from the group consisting of Ca, Sr, and Ba; M is any one of a Group 1 element of the periodic table and a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from the A and the X; n satisfies 0 < n < 1, y satisfies 0 < y < 1, m satisfies 0 ≤ m < 1, and n + y + m = 1,

[0037] In the formula (A), when each element contained in the composite oxide is represented by a subscript i (i includes at least A, X, M, O), the composition ratio of each element is represented by ni, and the Sanderson electronegativity of each element is represented by χi.

[0038] 〔1B〕 A composite oxide represented by the following general formula (1B):

[0039] A n X y M m O x (1B)

[0040] (In the general formula (1B), A is a rare earth element characterized by being at least a part in a state of III valence; X is any one of a Group 2 element, a Group 4 element, and a rare earth element, and represents an element different from the A; M is any one of a Group 2 element, a Group 4 element, and a rare earth element, and represents an element different from the A and the X; n satisfies 0 < n < 1, y is 1 - n, m satisfies 0 ≤ m ≤ 0.5, and x represents the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality).

[0041] 〔1C〕 A composite oxide containing metal elements represented by a composition of general formula (1C):

[0042] A n Xy M m (1C)

[0043] (In the general formula (1C), A is a rare earth element characterized by being in a state of being at least a part of which is in a valence of III; X is any one of a Group 2 element, a Group 4 element, and a rare earth element, and represents an element different from the A; M is any one of a Group 1 element, a Group 4 element, and a rare earth element, and represents an element different from the A and the X; n satisfies 0

[0044] 〔1D〕 The composite oxide according to any one of <1>, <1A>, <1B>, <1C>, characterized by being selected from Ce n La y O x , Pr n La y O x and Ce n Pr y O x (wherein n = 0.1 to 0.9, y = 0.1 to 0.9, and n + y = 1).

[0045] 〔1E〕 The composite oxide according to any one of <1>, <1A>, <1B>, <1C>, characterized by being selected from Ce n Ba y La m O x , La n Ba y Pr m O x and Pr n Ba y Ce m O x (wherein n = 0.1 to 0.99, y = 0.01 to 0.3, m = 0 to 0.9, and n + y + m = 1).

[0046] 〔1F〕 The composite oxide according to <1>, characterized by being selected from Ce 0.5 La 0.5 O x , Pr 0.5 La 0.5 O x , Ce 0.5 Pr 0.5 O x , Ce 0.85 La 0.15 O x , Ce 0.67 La0.33 O x , Ce 0.33 La 0.67 O x and Ce 0.15 La 0.85 O x .

[0047] 〔1G〕 The composite oxide according to [1], characterized by being selected from Ba 0.1 La 0.45 Ce 0.45 O x , Ba 0.3 Pr 0.35 Ce 0.35 O x , Ba 0.3 Ce 0.35 Pr 0.35 O x , Ba 0.3 La 0.35 Ce 0.35 O x , Ba 0.1 La 0.3 Ce 0.6 O x , Ba 0.1 La 0.6 Ce 0.3 O x , Ba 0.1 La 0.8 Ce 0.1 O x , Ba 0.05 La 0.475 Ce 0.475 O x , Ba 0.15 La 0.425 Ce 0.425 O x , Ba 0.1 Pr 0.45 Ce 0.45 O x and Ba 0.3 La 0.35 Pr 0.35 O x .

[0048] 〔1H〕 A binary system composite oxide comprising metal elements represented by the composition of general formula (1-1):

[0049] A n X y (1-1)

[0050] (in the general formula (1-1),

[0051] A is a lanthanoid element characterized by being at least a part or all in a state of III valence,

[0052] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A,

[0053] n satisfies 0 < n < 1,

[0054] y satisfies 0 < y < 1,

[0055] and n + y = 1.

[0056] 〔1K〕 A ternary complex oxide comprising metal elements represented by a composition of general formula (1-2):

[0057] A n X y M m (1-2)

[0058] (in the general formula (1-2),

[0059] A is a lanthanoid element characterized by being at least a part or all in a state of III valence,

[0060] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A,

[0061] M is any one of a Group 1 element of the periodic table and a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A and X,

[0062] n satisfies 0 < n < 1,

[0063] y satisfies 0 < y < 1,

[0064] m satisfies 0 < m < 1,

[0065] and n + y + m = 1.

[0066] 〔2〕 The complex oxide according to any one of 〔1〕 to 〔1K〕, characterized in that a ratio (A 3+ / A total ) of a number of moles of A in a state of III valence (A 3+ ) to a total number of moles of A (A total ) satisfies 0.1 ≤ A 3+ / A total ≤ 1.0.

[0067] 〔3〕 The composite oxide according to any one of <1> to <1K>, <2>, characterized by comprising a tetragonal or cubic solid solution.

[0068] 〔4-1〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, characterized in that at least one of the elements A, X, M contained in the composite oxide is a strong basic element having a value of the partial negative charge of oxygen (-δ O ) in the state of an oxide of 0.50 or greater.

[0069] 〔4-2〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, characterized in that the composition ratio of the elements contained in the composite oxide is represented by ni (i represents all of the elements contained in the composite oxide of A, X, M, O), and the Sanderson electronegativity of each element is represented by χi (i represents all of the elements contained in the composite oxide of A, X, M, O), and the value of the partial negative charge of oxygen (-δ O ) represented by the following formula (A) is 0.52 or greater:

[0070] ((Πχi ni ) 1 / Σni -5.21) / -4.75 · · (A)

[0071] 〔5〕 The composite oxide according to any one of <2>, <3>, <4-1>, <4-2>, characterized by being a binary system composite oxide represented by the following general formula (1-1) in place of the general formula (1) :

[0072] A n X y · · · (1-1)

[0073] (A, X, n, y are as defined in <1H>)

[0074] and the composite oxide is a solid solution of A and X.

[0075] 〔6〕 The composite oxide according to any one of <2>, <3>, <4-1>, <4-2>, characterized by being a ternary system composite oxide represented by the following general formula (1-2) in place of the general formula (1) :

[0076] A n X y M m · · · (1-2)

[0077] (A, X, M, n, y, m are as defined in <1K>)

[0078] Further, the composite oxide is in a state of being in solid solution with an oxide of one of X and M, and being mixed with an oxide of the other of X and M.

[0079] 〔7〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, <4-1>, <4-2>, <5>, and <6>, characterized in that X in the general formula (1), (1A), (1B), (1C), (1-1), and (1-2) is Ba, and the amount of carbonate ions contained in the composite oxide is 10 mol% or less as compared with Ba.

[0080] 〔7A〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, <4-1>, <4-2>, <5>, and <6>, characterized in that X in the general formula (1), (1A), (1B), (1C), (1-1), and (1-2) is Ba, and the amount of carbonate ions contained in the composite oxide is 1 mol% or less as compared with Ba.

[0081] 〔7B〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, <4-1>, <4-2>, <5>, and <6>, characterized in that X in the general formula (1), (1A), (1B), (1C), (1-1), and (1-2) is Ba, and the amount of carbonate ions contained in the composite oxide is 0.1 mol% or less as compared with Ba.

[0082] 〔7C〕 The composite oxide according to any one of <1> to <1K>, <2>, <3>, <4-1>, <4-2>, <5>, and <6>, characterized in that X in the general formula (1), (1A), (1B), (1C), (1-1), and (1-2) is Ba, and the amount of carbonate ions contained in the composite oxide is 0.01 mol% or less as compared with Ba.

[0083] 〔8〕 A composite oxide comprising metal elements represented by the general formula (1A):

[0084] A n X y M m ··(1A)

[0085] (In the general formula (1A),

[0086] A is a rare earth element characterized by being in a state of being at least a part or all of III valence,

[0087] X is any one of a Group 2 element, a Group 4 element, and a rare earth element of the periodic table, and represents an element different from A,

[0088] M is any one of Group 1 elements, Group 2 elements, Group 4 elements and rare earth elements in the periodic table, and represents an element different from the A and the X,

[0089] n satisfies 0 < n < 1,

[0090] y satisfies 0 < y < 1,

[0091] m satisfies 0 ≤ m < 1,

[0092] and n + y + m = 1).

[0093] 〔8A〕 The composite oxide according to 〔8〕, wherein the proportion (A 3+ / A total ) of the number of moles of A in the trivalent state (A 3+ ) to the total number of moles of A (A total ) satisfies 0.1 ≤ A 3+ / A total ≤ 1.0.

[0094] 〔8B〕 The composite oxide according to 〔8〕, wherein m = 0.

[0095] 〔8C〕 The composite oxide according to 〔8〕, characterized by being selected from the group consisting of Ce 0.5 La 0.5 O x , Ce 0.5 Zr 0.5 O x , Pr 0.5 La 0.5 O x , Pr 0.5 Zr 0.5 O x and Ce 0.5 Pr 0.5 O x .

[0096] 〔8D〕 The composite oxide according to 〔8〕, characterized by being selected from the group consisting of Ba 0.1 La 0.45 Ce 0.45 O x , Ba 0.3 Pr 0.35 Ce 0.35 O x , Ba 0.3 Ce 0.35 Pr 0.35 O x and Ba 0.3 La 0.35 Ce 0.35 O x .

[0097] 〔9〕 A composite oxide characterized by being represented by the following general formula (2):

[0098] A n X 1-n M m O x (2)

[0099] (in the general formula (2),

[0100] A is a rare earth element characterized by at least a part being in a state of III valence,

[0101] X is any one of a Group 2 element, a Group 4 element, and a rare earth element of the periodic table, and represents an element different from A,

[0102] M is any one of a Group 2 element, a Group 4 element, and a rare earth element of the periodic table, and represents an element different from A and X,

[0103] n satisfies 0 < n < 1,

[0104] m satisfies 0 ≤ m ≤ 0.5,

[0105] x represents the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality).

[0106] 〔9A〕 The composite oxide according to 〔9〕, wherein m = 0.

[0107] 〔9B〕 The composite oxide according to 〔9〕, characterized by being selected from Ce 0.5 La 0.5 O x .

[0108] 〔9C〕 The composite oxide according to 〔9〕, characterized by 0.5 < x ≤ 2.

[0109] 〔11〕 A metal support characterized by supporting a transition metal other than a Group 4 element on the composite oxide according to any one of 〔1〕 to 〔9C〕.

[0110] 〔11A〕 The metal support according to 〔11〕, wherein the transition metal is Ru.

[0111] 〔11B〕 The metal support according to 〔11〕, wherein the transition metal is Co.

[0112] 〔11C〕 The metal support according to 〔11〕, wherein the transition metal is one or more selected from the group consisting of Ru, Fe, Co, Ni, Rh, Pd, Os, Ir, and Pt.

[0113] 〔11D〕 The metal support according to item 〔11〕, wherein the transition metal is Ru and / or Co.

[0114] 〔11E〕 A metal support characterized in that a transition metal other than Group 4 is supported on a composite oxide containing a metal element represented by the general formula (1):

[0115] A n X y M m (1)

[0116] (In the general formula (1),

[0117] A is a lanthanoid element characterized by at least a part or all of it being in a state of III valence,

[0118] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A,

[0119] M is any one of a Group 1 element of the periodic table and a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A and X,

[0120] n satisfies 0 < n < 1,

[0121] y satisfies 0 < y < 1,

[0122] m satisfies 0 ≤ m < 1,

[0123] and n + y + m = 1).

[0124] 〔12〕 The metal support according to any one of items 〔11〕 to 〔11E〕, characterized in that, in the metal support, the ratio of the value (D ads ) of the dispersion degree of the transition metal other than Group 4 obtained by the H2 pulse chemisorption method to the value (D TEM ) of the dispersion degree of the transition metal predicted from the average particle diameter of the transition metal particles obtained from a TEM image satisfies: 0 < D ads / D TEM < 1.

[0125] 〔12A〕 The metal support according to item 〔11A〕, characterized in that the ratio of the value (D ads ) of the dispersion degree of Ru obtained by the H2 pulse chemisorption method to the value (D TEM ) of the dispersion degree of Ru predicted from the average particle diameter of the Ru particles obtained from a TEM image satisfies: 0 < D ads / D TEM < 1.

[0126] 〔12B〕 The metal support according to item 11B, characterized in that the ratio of the value (D ads ) of the Co dispersion degree obtained by the H2 pulse chemisorption method to the value (D TEM ) of the Co dispersion degree predicted from the average particle diameter of the Co particles obtained from the TEM image satisfies: 0 < D ads / D TEM < 1.

[0127] 〔13〕 The metal support according to any one of items 11 to 12B, characterized in that, when nitrogen is adsorbed to the supported transition metal, N≡N stretching vibration v1 of the nitrogen molecule interacting in the long axis direction is observed to be 2300 to 2000 cm -1 by infrared absorption spectroscopy, and / or weakened N≡N stretching vibration v2 of the nitrogen molecule interacting in the long axis direction with respect to the transition metal is observed to be 1900 to 1500 cm -1 .

[0128] 〔13A〕 The metal support according to any one of items 11 to 12B, characterized in that the v1 is 2100 to 2000 cm -1 and the v2 is 1700 to 1900 cm -1 .

[0129] 〔13B〕 The metal support according to any one of items 11 to 12B, characterized in that the transition metal is Ru.

[0130] 〔13C〕 The metal support according to any one of items 11 to 12B, characterized in that, when nitrogen is adsorbed and measured using an infrared spectrometer, an absorption peak from the nitrogen molecule after adsorption appears at 2200 cm -1 or less.

[0131] 〔13D〕 The metal support according to any one of items 11 to 12B, characterized in that, further, an absorption peak appears at 1900 to 1700 cm -1 .

[0132] 〔14〕 The metal support according to any one of items 11 to 13D, characterized in that the average particle diameter of the transition metal supported on the composite oxide is 100 nm or less.

[0133] 〔14A〕 The metal support according to any one of items 11 to 14, characterized in that the transition metal is Ru, and the average particle diameter of Ru supported on the composite oxide is 5 nm or less.

[0134] 〔14B〕 The metal support according to any one of <11> to <14>, characterized in that the transition metal is Co, and the average particle diameter of Co supported on the composite oxide is 100 nm or less.

[0135] 〔15〕 The metal support according to any one of <11> to <14B>, characterized in that the amount of the carbonate contained in the metal support is 10 mol% or less as compared with an element X of Group 2 of the periodic table selected from the group consisting of Ca, Sr and Ba.

[0136] 〔15A〕 The metal support according to any one of <11> to <15>, characterized in that the amount of the carbonate is 1 mol% or less.

[0137] 〔15B〕 The metal support according to any one of <11> to <15>, characterized in that the amount of the carbonate is 0.1 mol% or less.

[0138] 〔15C〕 The metal support according to any one of <11> to <15>, characterized in that the amount of the carbonate is 0.01 mol% or less.

[0139] 〔16〕 An ammonia synthesis catalyst characterized by using the metal support according to any one of <11> to <15C>.

[0140] 〔16A〕 The ammonia synthesis catalyst according to <16>, characterized in that the ammonia yield is 0.55% or more and the ammonia production rate is 10.0 mmol g -1 h -1 .

[0141] <Ammonia Activity Measurement Method>

[0142] While the temperature of the ammonia synthesis catalyst layer was maintained at 300°C, Ar was supplied, the pressure was increased to 1.0 MPa or 3.0 MPa by a back pressure valve at the outlet of the reaction tube, and the packing of Ar was stopped. While the pressure was maintained, H2, N2 was circulated at 90 mL / min, 30 mL / min (space velocity 72 Lh -1 g -1 ) respectively, the reaction atmosphere was switched, and 200 mL of a 1 to 100 mM (1, 5, 10, 25, 100 mM) aqueous sulfuric acid solution was added to a three-necked flask connected to a conductivity meter according to the level of NH3 synthesis activity. The mixed gas containing hydrogen, nitrogen, NH3 flowing out from the outlet of the reaction tube was bubbled in the aqueous sulfuric acid solution, and the amount of ammonia produced in the outlet gas was quantified by measuring the change in conductivity due to the reaction of NH3 with sulfuric acid.

[0143] 〔16B〕 An ammonia synthesis catalyst characterized by using a metal support that supports a transition metal other than Group 4 on a composite oxide containing a metal element represented by a composition of general formula (1):

[0144] A n X y M m (1)

[0145] (in the general formula (1),

[0146] A is a lanthanoid element characterized by at least a part or all of it being in a state of III valence,

[0147] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from the A,

[0148] M is any one of a Group 1 element of the periodic table, a Group 2 element selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from the A and the X,

[0149] n satisfies 0 < n < 1,

[0150] y satisfies 0 < y < 1,

[0151] m satisfies 0 ≤ m < 1,

[0152] and n + y + m = 1).

[0153] 〔17〕 A method for producing a composite oxide according to any one of 〔1〕 to 〔9C〕, comprising:

[0154] a mixing step of mixing an A precursor containing the A, an X precursor containing the X, and an M precursor containing the M to obtain a mixture; and

[0155] a firing step of firing the mixture at a temperature of 600°C or higher.

[0156] 〔17A〕 A method for producing a composite oxide according to 〔17〕, characterized in that, in the firing step, the mixture is fired at a temperature of 700°C or higher.

[0157] 〔17B〕 A method for producing a composite oxide according to 〔17〕 or 〔17A〕, characterized in that, in the firing step, the mixture is fired at a temperature of 800°C or lower.

[0158] 〔17C〕 A method for producing a composite oxide containing metal elements represented by a composition of general formula (1),

[0159] A n X y M m (1)

[0160] (in the general formula (1),

[0161] A is a lanthanoid element characterized by being at least partly or wholly in a state of III valence,

[0162] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A,

[0163] M is any one of a Group 1 element of the periodic table, a Group 2 element selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from A and X,

[0164] n satisfies 0 < n < 1,

[0165] y satisfies 0 < y < 1,

[0166] m satisfies 0 ≤ m < 1,

[0167] and n + y + m = 1)

[0168] a method for producing the composite oxide, comprising:

[0169] a mixing step of mixing an A precursor containing the A, an X precursor containing the X, and an M precursor containing the M to obtain a mixture; and

[0170] a firing step of firing the mixture at a temperature of 600°C or higher.

[0171] a method for producing a metal support, the metal support being the metal support described in any one of to, comprising:

[0172] a mixing step of mixing an A precursor containing the A, an X precursor containing the X, and an M precursor containing the M to obtain a mixture;

[0173] a firing step of firing the mixture at a temperature of 600°C or higher to obtain a support composed of a composite oxide;

[0174] a supporting step of supporting a compound containing the transition metal on the composite oxide to prepare a pre-reduction treatment support; and

[0175] a reduction step of performing a reduction treatment on the pre-reduction treatment support at a temperature of 400°C or higher.

[0176] 〔18A〕 The method for producing a metal support according to any one of 〔18〕, wherein in the calcination step, the mixture is calcined at a temperature of 700°C or higher.

[0177] 〔18B〕 The method for producing a metal support according to any one of 〔18〕 or 〔18A〕, wherein in the calcination step, the mixture is calcined at a temperature of 800°C or lower.

[0178] 〔18C〕 The method for producing a metal support according to any one of 〔18〕 to 〔18B〕, wherein in the reduction step, the mixture is subjected to a reduction treatment at a temperature of 350°C or higher and in an atmosphere containing hydrogen for 2 hours or longer.

[0179] 〔18D〕 The method for producing a metal support according to any one of 〔18〕 to 〔18C〕, wherein in the reduction step, the reduction-treated support is calcined at a temperature of 500°C or higher and in an atmosphere containing hydrogen for 2 hours or longer.

[0180] 〔18E〕 A method for producing a metal support, the metal support being supported on a composite oxide containing a metal element represented by a composition of general formula (1):

[0181] A n X y M m (1)

[0182] (in the general formula (1),

[0183] A is a lanthanoid element characterized by being at least a part or all in a state of III valence,

[0184] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from A,

[0185] M is any one of a Group 1 element of the periodic table, a Group 2 element selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from A and X,

[0186] n satisfies 0 < n < 1,

[0187] y satisfies 0 < y < 1,

[0188] m satisfies 0 ≤ m < 1,

[0189] and n + y + m = 1)

[0190] the method for producing a metal support comprising:

[0191] mixing step of mixing an A precursor containing the A, an X precursor containing the X, and an M precursor containing the M to obtain a mixture;

[0192] firing step of firing the mixture at a temperature of 600°C or higher to obtain a support composed of a composite oxide;

[0193] supporting step of supporting a compound containing the transition metal on the composite oxide to prepare a reduction treatment pre-support; and

[0194] reduction step of subjecting the reduction treatment pre-support to a reduction treatment at a temperature of 400°C or higher.

[0195] 〔19〕A method for producing ammonia, which is a method for producing ammonia by bringing hydrogen and nitrogen into contact with a catalyst, characterized in that the catalyst is the ammonia synthesis catalyst according to any one of 〔16〕 to 〔16B〕.

[0196] 〔19A〕The method for producing ammonia according to 〔19〕, characterized in that the reaction temperature is 300 to 550°C and the reaction pressure is 0.1 to 20 MPa.

[0197] 〔19B〕The method for producing ammonia according to any one of 〔19〕 to 〔19A〕, characterized in that the reaction temperature is 300 to 450°C and the reaction pressure is 0.1 to 10 MPa.

[0198] 〔19C〕A method for producing ammonia, which is a method for producing ammonia by bringing hydrogen and nitrogen into contact with a catalyst, characterized in that the catalyst is an ammonia synthesis catalyst using a metal support in which a transition metal other than Group 4 is supported on a composite oxide containing a metal element represented by the general formula (1):

[0199] A n X y M m (1)

[0200] (in the general formula (1),

[0201] A is a lanthanoid element characterized by being at least a part or all in a state of III valence,

[0202] X is any one of a Group 2 element of the periodic table and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and represents an element different from the A,

[0203] M is any one of a Group 1 element of the periodic table, a Group 2 element selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from the A and the X,

[0204] n satisfies 0 < n < 1,

[0205] y satisfies 0 < y < 1,

[0206] m satisfies 0 ≤ m < 1.

[0207] And n+y+m=1).

[0208] The effects of the invention

[0209] According to the present invention, a composite oxide supported on a catalyst metal such as ruthenium can be provided to further enhance the activity of ammonia synthesis. By using it as a support for a catalyst in ammonia synthesis, ammonia can be produced with a high yield under milder conditions compared to the Hubble-Bosch process. Furthermore, according to the present invention, a metal support for supporting a catalyst metal such as ruthenium and further enhancing the activity of ammonia synthesis, as well as a catalyst for ammonia synthesis, can be provided. Further, according to the present invention, a method for manufacturing such a composite oxide, a method for manufacturing a metal support with enhanced ammonia synthesis activity, and a method for manufacturing ammonia can be provided. Attached Figure Description

[0210] Figure 1 These are the XRD patterns of different Ru-supported composite oxides.

[0211] Figure 2 Ru / La is subjected to different temperatures 0.5 Ce 0.5 O 1.75 After reduction, HR-TEM and EDX mapping images of Ru-supported composite oxides exposed to air, and a histogram of Ru particle diameters. Figure 2 (a) is LaCeO x STEM image at 500℃ Figure 2 (b) is LaCeO x EDX mapping at 500℃ red Figure 2 (c) is LaCeO x A bar chart of _500℃red, Figure 2 (d) is LaCeO x STEM image at 650℃ Figure 2 (e) is LaCeO x EDX mapping of _650℃red Figure 2 (f) is LaCeO x A bar chart of _650℃red, Figure 2 (g) is LaCeO x STEM image at 800℃ Figure 2 (h) is LaCeO xEDX mapping of 800°C red, Figure 2 (i) is LaCeO x Histogram of 800°C red.

[0212] Figure 3 is an IR spectrum of the metal support after reduction treatment, after addition of N2 at room temperature.

[0213] Figure 4 is a graph showing the relationship between the ammonia generation rate and the reduction treatment temperature.

[0214] Figure 5 is a table showing the relationship between the ammonia generation rate H / Ru, the degree of reduction of the specific surface area, and the change in the Ru particle diameter, which are caused by the difference between the firing temperature of the composite oxide and the reduction treatment temperature of the metal support.

[0215] Figure 6 is a TEM image of Ru / Ba 0.1 La 0.45 Ce 0.45 O x and Ru / La 0.5 Ce 0.5 O x XRD patterns of Ru / Ba 0.1 La 0.45 Ce 0.45 O x

[0216] Figure 7 is an image of the surface of Ru / Ba 0.1 La 0.45 Ce 0.45 O x analyzed by fluorescence X-ray analysis using a chromatic aberration correction transmission electron microscope. DETAILED DESCRIPTION

[0217] The composite oxide of the present application contains metal elements represented by the composition of the following general formula (1):

[0218] A n X y M m (1).

[0219] In the composite oxide,

[0220] (1) A is a rare earth element characterized by at least a part or all in a state of III valence, and particularly preferably a lanthanoid element characterized by at least a part or all in a state of III valence.

[0221] (2) X is selected from a group consisting of a Group 2 element, a Group 4 element, or a rare earth element of the periodic table, and is an element different from A, and particularly preferably any one of a Group 2 element and a lanthanoid element selected from the group consisting of Ca, Sr, and Ba, and is an element different from the A,

[0222] (3) M is selected from the group consisting of an element of Group 1 of the periodic table, an element of Group 2 of the periodic table, an element of Group 4, and a rare earth element, and is an element different from A and X, and particularly, it is preferable that it is any one of an element of Group 1 of the periodic table and an element of Group 2 selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and is an element different from the A and the X.

[0223] (4) n satisfies 0 < n < 1, y satisfies 0 < y < 1, m satisfies 0 ≤ m < 1, and n + y + m = 1.

[0224] The composite oxide of the present application, particularly preferably contains metal elements represented by the composition of the following general formula (1):

[0225] A n X y M m (1)

[0226] (in the general formula (1),

[0227] A is a lanthanoid element characterized by being in a state of at least a part or all of III valence,

[0228] X is any one of an element of Group 2 of the periodic table selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from the A,

[0229] M is any one of an element of Group 1 of the periodic table and an element of Group 2 selected from the group consisting of Ca, Sr, and Ba, and a lanthanoid element, and represents an element different from the A and the X,

[0230] n satisfies 0 < n < 1,

[0231] y satisfies 0 < y < 1,

[0232] m satisfies 0 ≤ m < 1,

[0233] and n + y + m = 1.

[0234] Alternatively, the composite oxide of the present application can contain metal elements represented by the general formula (1A):

[0235] A n X y M m (1A)

[0236] (in the general formula (1A),

[0237] A is a rare earth element characterized by being in a state of at least a part or all of III valence,

[0238] X is any one of a Group 2 element, a Group 4 element and a rare earth element, and represents an element different from the A,

[0239] M is any one of a Group 1 element, a Group 4 element and a rare earth element, and represents an element different from the A and the X,

[0240] n satisfies 0

[0241] y satisfies 0

[0242] m satisfies 0

[0243] and n + y + m = 1.

[0244] Further, the composite oxide of the present application can be a composite oxide represented by the following general formula (2):

[0245] A n X y M m O x (2)

[0246] (In the general formula (2),

[0247] A is a rare earth element characterized by being in a state of at least a part or all of the III valence,

[0248] X is any one of a Group 2 element, a Group 4 element and a rare earth element, and represents an element different from the A,

[0249] M is any one of a Group 2 element, a Group 4 element and a rare earth element, and represents an element different from the A and the X,

[0250] n satisfies 0

[0251] y is 1―n,

[0252] m satisfies 0

[0253] x represents the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality.

[0254] Further, at least one of the elements A, X, M constituting the composite oxide containing the metal elements represented by the composition of the general formula (1) is a strong basic element having a value of the partial negative charge (-δ O ) of oxygen in the state of an oxide of 0.50 or more.

[0255] Element A is a rare earth element, and at least part of it is in a state of III valence. Here, "at least part of it is in a state of III valence" means, for elements that can only take the III valence, that state; for elements that can take the III valence and other valences (e.g., IV valence), it means that at least part of it is in a state of III valence. That is, element A includes elements that can only take the III valence, and elements that can take both III and IV valences, and at least part of them are in a state of III valence. To ensure that at least part of an element capable of taking both III and IV valences is in a state of III valence, a portion of the IV valence is reduced to III valence through a reduction process described below.

[0256] In this invention, the catalyst contains at least one of elements A, X, and M, which is a strongly basic element that exhibits high basicity in its oxide state, thus enhancing the activity of the ammonia synthesis catalyst. The principle is summarized below.

[0257] The basicity (Lewis basicity) of metal oxides is related to their electron-donating ability. That is, a substance with a higher electron-donating ability can be considered to exhibit stronger basicity. Basically, in oxides, oxygen acts as an electron donor, so the amount of charge carried by oxygen in an oxide, i.e., the partial negative charge of oxygen, can be used as an indicator of basicity. In fact, non-patent literature (Sanderson, Inorganic Chemistry (Vol. 1), Hirokawa Shoten (1975), p. 276, Table 12.7) shows that the value of the partial negative charge of oxygen is strongly correlated with the acidity or basicity exhibited by the oxide.

[0258] The method for calculating the partial negative charge of oxygen is described in non-patent literature (Sanderson, *Inorganic Chemistry (Volume 1)*, Hirokawa Shoten (1975), p. 122, Table 6.7, pp. 126-128). First, determine the composition ratio of each element in the composite oxide. For example, "Ce..." 0.5 La 0.5 O 1.75 The value of La is 0.5, and this value is denoted as ni (where i is the corresponding element). The electronegativity of each element is denoted as χi. Then, the geometric mean of the electronegativity of all atoms constituting the composite oxide is calculated using (Π(χini))^(1 / Σni). Next, to calculate the change in the electronegativity of oxygen, the difference between the geometric mean and the electronegativity of oxygen (5.21) is calculated. Finally, the change in the electronegativity of oxygen is divided by the change in electronegativity when each oxygen atom gains one electron (-4.75). Through the above calculations, the partial negative charge of oxygen shown in the composite oxide can be calculated. A detailed description can be found in the examples described below.

[0259] Summarizing the above, regarding the value of the partial negative charge of oxygen of the composite oxide, when the composition ratio of each element included in the composite oxide is denoted as n i (i denotes all elements in the composite oxide including at least A, X, M, O) and the electronegativity of each element is denoted as χ i (i denotes all elements in the composite oxide including at least A, X, M, O), the value of the partial negative charge of oxygen represented by the following formula (A) is preferably 0.52 or greater.

[0260] ((Πχi ni ) 1 / Σni -5.21) / -4.75 (A)

[0261] The value of the partial negative charge of oxygen of the composite oxide is preferably 0.52 or greater, more preferably 0.55 or greater, and particularly preferably 0.57 or greater. When the value of the partial negative charge of oxygen of the composite oxide is 0.52 or greater, there is a tendency for the ammonia synthesis activity to be high. The upper limit of the value of the partial negative charge of oxygen of the composite oxide is not particularly limited, and is theoretically about 0.70 at the maximum.

[0262] In the case where A is an element that can take the III valence such as La, it is a strongly basic metal element. Therefore, electrons are generated from the base point of the composite oxide (the support), and the electrons are in turn supplied to the nitrogen molecule through the transition metal (Ru, etc.) supported on the composite oxide, weakening the nitrogen triple bond. Thus, it is possible to lower the energy for breaking the nitrogen molecule triple bond in the rate-determining stage of the ammonia synthesis reaction, and it is possible to improve the ammonia synthesis activity of the metal support (the catalyst).

[0263] In the case where A is an element that can take the III valence and the IV valence such as Ce, it is a strongly basic metal element in the case of the III valence, but the degree of basicity is lower than in the case of the III valence in the case of the IV valence. As described below, Ce is in the IV valence at the time point of mixing the raw materials and firing to form the composite oxide, but at least a part or all of it can become the III valence and can become a strongly basic element through reduction treatment, etc. described below. Thus, based on the same principle as in the case where A is La described above, it is possible to improve the ammonia synthesis activity of the metal support. Further, by reducing the element in the IV valence to the III valence and re-oxidizing the element to the IV valence, it is possible to generate electrons that are in turn supplied to the nitrogen molecule through the transition metal (Ru, etc.), and it is possible to improve the ammonia synthesis activity of the metal support.

[0264] Although the above describes the case where element A is a strong basic element, element X and element M described below can also be strong basic elements. In particular, in the case of a composite oxide of a binary system composed of elements A and X, it is more preferable that both of elements A and X are strong basic. In the case of a composite oxide of a ternary system composed of elements A, X, and M, there is a case where the basicity of element M is stronger than that of elements A and X. In particular, in the case where element X and / or M is an element of Group 2 of the periodic table selected from Ca, Sr, and Ba, there is a tendency that the basicity is higher than that of element A (rare earth element).

[0265] Note that, in the case where the strong basic element, particularly element M is an element of Group 2 of the periodic table, it is easy to react with carbon dioxide in the atmosphere to form a metal carbonate and a hydroxide, and the metal carbonate and the hydroxide decrease the basicity of the composite oxide, which is a cause of decrease in the ammonia synthesis activity of the catalyst. For example, Ba is easy to form BaCO3 and Ba(OH)2 in the atmosphere, which decreases the ammonia synthesis activity. Therefore, it is preferable that the metal carbonate and the hydroxide contained in the ammonia synthesis catalyst are as little as possible. In order to reduce the carbonate, it is preferable to perform reduction treatment as described below, whereby the carbonate and the hydroxide contained in the catalyst are decomposed, and the decrease in the basicity can be prevented. The amount of the carbonate contained in the metal support is not particularly limited as long as it is within a range not to hinder the ammonia synthesis activity, for example, 10 mol% or less, preferably 1 mol% or less, more preferably 0.1 mol% or less, and still more preferably 0.01 mol% or less, compared with element X of Group 2 of the periodic table selected from the group consisting of Ca, Sr, and Ba.

[0266] As a method for quantifying the amount of the metal existing in the form of a carbonate, methane or the like produced by hydrogenation of the carbonate species by heating the catalyst under hydrogen flow is detected by a mass spectrometer or a hydrogen flame ionization detector, and the amount existing in the form of a carbonate is quantified by conversion.

[0267] In addition, infrared absorption spectroscopy, which is highly sensitive to the carbonate of the metal, can also be used. The absorption intensity of the peak of the tail number characteristic of the absorption of the carbonate is measured by irradiating infrared light to the catalyst, and the amount of the carbonate contained in the catalyst can be quantified. For example, the position of the peak that can be used for quantification of Ba carbonate is around 3000 cm -1 , around 2450 cm -1 , around 1750 cm -1 , around 1480 cm -1 , around 1060 cm -1 , and the like.

[0268] When A is a rare earth element with a valence of III or higher (above IV), the total number of moles of A (A) total The ratio of (A) to 3+ / A total Preferably, 0.1 ≤ A 3+ / A total ≤1.0. A 3+ / A total The lower limit of the value is 0.1 or higher, preferably 0.2 or higher, and more preferably 0.3 or higher. A 3+ / A total There is no particular limit to the upper limit of the value, but it is preferred to be closer to 1.0, preferably 0.8 or higher, more preferably 0.9 or higher, and particularly preferably 0.95 or higher. If A 3+ / A total When the value is above 0.1 and below 0.95, it exhibits excellent performance per unit weight of catalyst when used as a catalyst for ammonia synthesis. Ce is an example of such a rare earth element.

[0269] On the other hand, when A is a rare earth element that can only take the III valence, satisfying A 3+ / A total =1.00. As such rare earth elements, La can be listed.

[0270] In the case where A is a rare earth element capable of valence III and higher (valence IV and above), in order to obtain the target A 3+ / A total The value of A can be obtained using various chemical reduction methods. The simplest method is to heat the metal support under a flow of hydrogen; by changing the temperature and heating time, A can be reduced. 3+ / A total The value can be controlled to be arbitrary. Alternatively, by mixing inert gases such as nitrogen and argon to change the hydrogen concentration, it is also possible to control A... 3+ / A total The control can be any value.

[0271] As such element A, the lanthanide elements can be listed, preferably Ce, Pr, Tb, and La, more preferably Ce and La, and most preferably Ce.

[0272] The element X constituting the complex oxide of general formula (1) is different from the other element A constituting the complex oxide and also different from the element M, if it is selected from the group consisting of the group 2 elements of the periodic table, i.e. Mg, Ca, Sr, Ba, the group 4 elements of the periodic table, i.e. Ti, Zr or Hf, or the rare earth elements, i.e. Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu. In the case where the element M is a group 2 element of the periodic table, it is preferably selected from the group consisting of Ca, Sr, Ba. Further, in the case where the element M is a rare earth element, it is preferably a lanthanoid element.

[0273] The element M constituting the complex oxide of general formula (1) is different from the other element A constituting the complex oxide and also different from the element X, if it is selected from the group consisting of the group 1 elements of the periodic table, i.e. Na, K, Rb, Cs, Fr, the group 2 elements of the periodic table, i.e. Mg, Ca, Sr, Ba, the group 4 elements of the periodic table, i.e. Ti, Zr or Hf, or the rare earth elements, i.e. Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu. In the case where the element X is a group 2 element of the periodic table, it is preferably selected from the group consisting of Ca, Sr, Ba. Further, in the case where the element X is a rare earth element, it is preferably a lanthanoid element. In particular, from the viewpoint of the ammonia synthesis activity, the element M is preferably Ba.

[0274] Preferably, X and M can be selected from the group consisting of Zr and La. The complex oxide in the present application can contain 2 kinds of the group 4 elements of the periodic table or the rare earth elements as X and M, or can contain only 1 kind of the group 4 elements of the periodic table or the rare earth elements as X (m = 0 in general formula (1)).

[0275] At least one of the elements A, X, M, preferably a strong basic element having a value of the partial negative charge of oxygen (-δ O ) of 0.50 or more in the state of an oxide. Two or more of the elements A, X, M, particularly preferably all of them, are a strong basic element having a value of the partial negative charge of oxygen (-δ O ) of 0.50 or more in the state of an oxide. Two or more of the elements A, X, M, particularly preferably all of them, are a strong basic element having a value of the partial negative charge of oxygen (-δ O ) of 0.50 or more in the state of an oxide.

[0276] Here, the partial negative charge of oxygen (-δ O ) is a value described in Table 12.7 of Non-Patent Literature (SANDERSON, Inorganic Chemistry (I), KyowITSU Shuppan-sha (1975), p. 276), and a value not described therein can be calculated by the above-described calculation of the partial negative charge of oxygen. Representative oxides and valence numbers, partial negative charges of oxygen (-δO ).

[0277]

Table 1

[0278] Oxide Valence partial negative charge of oxygen (-δ O )]]> BaO II valence 0.67 La2O3 III valence 0.56 Pr2O3 III valence 0.55 Ce2O3 III valence 0.55 Tb2O3 III valence 0.54 Tb4O7 III + IV valence 0.50 CeO2 IV valence 0.49 PrO2 IV valence 0.48 ZrO2 IV valence 0.44

[0279] Among the elements A, X, M, in the case of Ba, La, and the like in which the valence number of the oxide is only one kind and the partial negative charge of oxygen of the oxide is 0.50 or more, these elements are strong basic elements. In the case of Ce, Pr, Tb, and the like in which the valence number of the oxide can take two or more kinds, the value of the partial negative charge of oxygen (-δ O ) calculated from the ratio of the valence number of the element contained in the composite oxide is preferably 0.50 or more. For example, in Pr, in the case where all of the Pr contained in the composite oxide is in the IV valence, the value of the partial negative charge of oxygen (-δ O ) is 0.48. On the other hand, in the case where all of the Pr is in the III valence, the value of the partial negative charge of oxygen (-δ O ) is 0.55, and thus is more preferable than the above Pr (IV valence) in terms of the ammonia synthesis activity. In the case where both the III valence and the IV valence are present in the element, the value of the partial negative charge of oxygen (-δ O ) can be calculated in the same manner as in the case of the partial negative charge of oxygen in the above composite oxide. That is, if the ratio (composition ratio) of the element in the III valence to the element in the IV valence is known, the content of oxygen that makes the oxide electrically neutral is determined, and thus the geometric mean can be calculated by Formula (A). Further, in the case where two or more kinds of elements in which both the III valence and the IV valence are present are contained, such as a composite oxide composed of Ce and Pr, by using the ratio of the element in the III valence to the element in the IV valence in each element, the content of oxygen that makes the oxide electrically neutral can be determined. In order to find the ratio of the element in the III valence to the element in the IV valence in each element, methods such as diffraction line shift of XRD, absorption spectroscopy, and the like can be used. With respect to an element in which a valence number other than the III valence and the IV valence is present, the value of the partial negative charge of oxygen (-δ O ) can also be calculated in the same manner.

[0280] In the case where the composite oxide of the present application is represented by General Formula (1), the range of n, y, m, x is as follows:

[0281] n in General Formula (1) representing the ratio of the element A in the composite oxide satisfies 0 < n < 1, preferably 0.05 < n < 0.95, more preferably 0.1 < n < 0.9, and particularly preferably 0.35 ≤ n ≤ 0.5.

[0282] Y in general formula (1) representing the proportion of element X in the composite oxide satisfies 0 < y < 1, preferably 0.05 < y < 0.95, more preferably 0.1 < y < 0.9, and particularly preferably 0.35 ≤ y ≤ 0.5.

[0283] M in general formula (1) representing the proportion of element X in the composite oxide satisfies 0 ≤ m < 1, and m in general formula (2) satisfies 0 ≤ m ≤ 0.5. In general formulae (1) and (2), 0 < m < 0.5 is preferable, 0.05 ≤ m ≤ 0.45 is more preferable, and 0.1 ≤ m ≤ 0.3 is particularly preferable. In the case where m = 0, the composite oxide is composed only of A, X, and O.

[0284] X in general formula (2) representing the proportion of oxygen O in the composite oxide represents the number of oxygen atoms necessary for the composite oxide to maintain electrical neutrality. Although x depends on the kinds of A, X, and M elements, it is generally in the range of 0.5 < x ≤ 2, and particularly in the range of 1 < x ≤ 2.

[0285] The composite oxide containing metal elements represented by general formula (1) and the composite oxide of general formula (2) used in the present application are preferably tetragonal or cubic solid solutions. These crystal structures have high symmetry, and the crystal lattices have flexibility, and thus the crystal structure can be maintained even if the proportion of III valence in element A changes or the number of oxygen atoms changes.

[0286] In the case where, for example, La 0.5 Ce 0.5 O 1.75 In the case of a support containing two kinds of metal elements, and in the case where these elements are a composite of lanthanoid elements, a solid solution in which the elements are uniformly dissolved is generally formed. Also, the Ru particles are in direct contact with the surface thereof. In the case where Ce is reduced, both La and Ce are elements that are strongly basic in the state of an oxide, and thus it can be inferred that the number of active sites with Ru is large, and the ammonia synthesis activity is increased.

[0287] On the other hand, in the case where, for example, Ba 0.1 La 0.45 Ce 0.45 O xIn the case of such a ternary carrier containing three kinds of metal elements, the atomic radius of Ba is larger than that of La and Ce. In this case, when the firing temperature of the raw material mixture is high, for example, the firing temperature exceeds 1000°C, all of the elements are uniformly solid-solved, forming a crystal structure of perovskite type. On the other hand, when the firing temperature of the raw material mixture is low, Ba is a larger element, and thus it is difficult to be solid-solved with other elements. Therefore, a structure in which Ba is unevenly mixed in a solid solution of La and Ce, with a part of Ba exposed to the surface of the solid solution of La and Ce. Ba is a strong alkaline element having a higher value of partial negative charge of oxygen than La and Ce, and thus in the carrier in which Ba is unevenly exposed, the contact area of Ba with Ru increases, and the active sites increase. Therefore, it is presumed that the ammonia synthesis activity increases.

[0288] In the case where the partial negative charge of oxygen of the present application is calculated, (a) can be calculated from the partial negative charge of oxygen in the state of an oxide, and (b) can be calculated from the following formula (A) when the composition ratio of each element included in the composite oxide is represented by ni (i represents all of the elements included in the composite oxide of A, X, M, and O), and the Sanderson electronegativity of each element is represented by χi (i represents all of the elements included in the composite oxide of A, X, M, and O).

[0289] ((Πχi ni ) 1 / Σni -5.21) / -4.75··(A)

[0290] In the case where the composite oxide of the present application forms a uniform composite oxide, the method of (b) is more preferable, and in the case where the composite oxide of the present application forms a non-uniform composite oxide, the method of (a) is preferably performed, and in this case, the result of the element having the largest absolute value among the partial negative charges of oxygen of the individual elements can be used. In the present specification, the value of the partial negative charge of oxygen of the composite oxide is calculated by the method of (b) described above.

[0291] The metal carrier of the present application is characterized in that a transition metal other than Group 4 is supported on the composite oxide of the present application. As the transition metal, one or more selected from the group consisting of Ru, Fe, Co, Ni, Rh, Pd, Os, Ir, and Pt is preferable from the viewpoint of high catalyst activity, and Ru and / or Co is more preferable. The amount ratio of the transition metal to the composite oxide can be determined in consideration of the catalyst activity and the cost of the transition metal, and for example, the ratio of the transition metal to the entire metal carrier is preferably in the range of 0.1 to 50% by weight, and more preferably in the range of 5.0 to 30% by weight.

[0292] The Ru dispersion value (D ads ) obtained by the H2 pulse chemisorption method is preferably less than 1.0. The ratio of the Ru dispersion value (D TEM ) obtained by the H2 pulse chemisorption method to the Ru dispersion value (D ads ) predicted from the average particle diameter of the Ru particles obtained from the TEM image is preferably 0 < D TEM / D ads TEM

[0293] The Ru dispersion value is the ratio of the number of hydrogen atoms corresponding to the number of Ru atoms exposed on the surface of the metal support to the total number of Ru atoms contained in the metal support. The Ru dispersion value can be obtained from the hydrogen adsorption amount of the metal support on which Ru is supported.

[0294] Specifically, assuming that one Ru atom adsorbs one H atom, the ratio of the number of hydrogen atoms (H) corresponding to the number of Ru atoms exposed on the surface of the metal support to the total number of Ru atoms supported by the metal support (H / Ru) is the Ru dispersion value. In the present application, the Ru dispersion value based on the hydrogen adsorption amount is denoted as D ads By comparing metal supports on which the same amount (the same number of atoms) of Ru is supported, it can be found that the higher the Ru dispersion value, the greater the number of catalyst active sites.

[0295] It is also known that, assuming that the shape of the Ru particles is a cube, the Ru dispersion value can be geometrically obtained using the average particle diameter (d, in nm) of Ru obtained by TEM observation (see the reference "Dictionary of Catalysts"). This calculation method can be represented by the general formula (4). The average particle diameter of Ru can be calculated by randomly extracting 100 to 150 points of Ru particles from the TEM image, measuring the particle diameter of each of the particles, and then calculating the average value thereof. In the present application, the Ru dispersion value obtained based on the general formula (4) is denoted as D TEM .

[0296] D TEM = 1.113 / d (4)

[0297] Therefore, D ads / D TEM is less than 1 means that a part of the Ru particles, mainly the interface between the particles and the composite oxide (the support), is covered with the support material, and the adsorption of H atoms to the surface of the Ru particles is hindered. Such a phenomenon is known as a Strong Metal Support Interaction (SMSI) phenomenon, which can be found in the case where there is a strong interaction between the supported metal and the support. It is known that the driving force of the SMSI is, for example, the generation of a reduced support such as Ru / CeO 2-x .

[0298] In the metal-support of the present application formed by supporting the metal ruthenium on the composite oxide, the average particle diameter of Ru is preferably 5 nm or less. More preferably, it is 3 nm or less, and still more preferably, it is 2 nm or less. The smaller the particle diameter of Ru, the more the number of active sites in the case of use as an ammonia synthesis catalyst, and thus it is advantageous. The lower limit of the average particle diameter of Ru is not particularly limited, and for example, it is 0.1 nm or more, or 0.5 nm or more.

[0299] In addition, in the case of supporting the metal cobalt on the composite oxide, the average particle diameter of Co is preferably 100 nm or less. More preferably, it is 50 nm or less, and still more preferably, it is 30 nm or less. The smaller the particle diameter of Co, the more the number of active sites in the case of use as an ammonia synthesis catalyst, and thus it is advantageous. The lower limit of the average particle diameter of Co is not particularly limited, and for example, it is 0.5 nm or more, or 1 nm or more. In the case of Co as well as in the case of Ru, the value of the Co dispersion degree (D ads ) obtained by the H2 pulse chemisorption method is preferably in the range of 0 < D TEM < 1 with respect to the value of the Co dispersion degree (D ads ) predicted from the average particle diameter of the Co particles obtained from the TEM image. TEM

[0300] The composite oxide of general formula (1) used in the present application has a part or all of A being trivalent, and a supported catalyst Ru is a fine particle having an average particle diameter of 5 nm or less. Therefore, under mild ammonia synthesis conditions (300 to 500°C, 0.1 to 20 MPa), a very high ammonia synthesis rate (for example, 13.4 mmol g -1 h -1 of Ru at 0.1 MPa, or 31.3 mmol g -1 h -1 of Ru at 1 MPa at 350°C) is shown.

[0301] The composite oxide of the present application having a part of A being trivalent can be obtained by reduction treatment of a thermally stable composite oxide supporting a Ru catalyst at a high temperature. The technique of reduction treatment of a Ce oxide supporting Ru has been known before, but it has been understood until now that if the reduction treatment temperature exceeds 500°C, the ammonia synthesis rate of the catalyst decreases (non-patent literature 1).

[0302] In this regard, the inventors found that, in the case of La 0.5 Ce 0.5 O 1.75 ​Represented by metal supports in a reduced state, the ammonia synthesis rate of Ru-supported composite oxides can be increased by reduction treatment at high temperatures exceeding 500°C, reaching a peak at a reduction treatment temperature of approximately 650°C. It was found that using a Ce-containing composite oxide as a support yields a catalyst exhibiting higher activity compared to using only Ce oxides as a support.

[0303] It should be noted that, for the sake of brevity, in this specification, "La carrying Ru" will be referred to as "La". 0.5 Ce 0.5 O 1.75 The metal support referred to in the figure is denoted as "Ru / La". 0.5 Ce 0.5 O 1.75 The product of the reduction treatment of the metal oxide is denoted as "Ru / La". 0.5 Ce 0.5 O x Other supports are also represented using the same notation. Here, x means that as a portion of Ce is reduced from IV to III, the molar ratio of oxygen during firing decreases from 1.75 to x.

[0304] For example, the composite oxide La of the present invention, which is a composite oxide of CeO2 and La2O3 and was reduced at an unprecedented high temperature of 650°C, is an example of this invention. 0.5 Ce 0.5 O x It is a solid solution of tetragonal or cubic crystals. Furthermore, the Ru catalyst supported on this composite oxide exhibits ammonia synthesis activity comparable to the highest-activity catalyst reported to date. This structure and state of the catalyst, resulting from the effect of reduction temperature, can be elucidated through a combination of various characterization methods, including scanning transmission electron microscopy (STEM) image processing and chemisorption assays.

[0305] As shown in Table 2, the reduction of Ru / La at 500℃ 0.5 Ce 0.5 O 1.75 The obtained metal support (Ru / La) 0.5 Ce 0.5 O x The ammonia synthesis rate at 1.0 MPa and 350 °C, compared with the ammonia synthesis rate obtained by reducing Ru / La₂O₃ at 500 °C and the ammonia synthesis rate obtained by reducing Ru / CeO₂ at 500 °C. x Compared to the previous method, this is more than 1.7 times higher. This indicates that the rate of ammonia synthesis is increased by using a composite oxide of La2O3 and CeO2.

[0306] like Figure 1 As shown, in the XRD pattern of Ru / La₂O₃, in addition to the smaller peaks caused by La₂O₃, numerous peaks from LaOOH and La(OH)₃ were observed. On the other hand, in Ru / La… 0.5 Ce 0.5 O x In the XRD pattern, peaks from a cubic crystal structure with a smaller lattice than CeO2 were observed, and no other peaks from impurities such as LaOOH and La(OH)3 were observed. These results indicate that the unreduced La 0.5 Ce 0.5 O 1.75 The formation of complex oxides hinders the adsorption of water to La₂O₃ and the crystal growth of the acidic support. In fact, the reduction of La at 500℃... 0.5 Ce 0.5 O 1.75 The specific surface area of ​​the obtained composite oxide is 47 m². 2 g -1 The products of reducing Ru / CeO2 at 500℃ and 650℃ (24 and 20 m, respectively) 2 g -1 Compared to that, it is far larger. In La 0.5 Ce 0.5 O x The increased specific surface area is likely due to the simultaneous presence of different cations on the surface of the composite oxide. These results indicate that by using a composite oxide of CeO2 and La2O3, the number of active sites for Ru increases, and the reduction of Ru / La at 500 °C is facilitated. 0.5 Ce 0.5 O x The resulting metal-supported material can lead to a very high ammonia synthesis rate.

[0307] Thus, it can be considered that in the metal support of the present invention, the reduced thermal stability La 0.5 Ce 0.5 O x By stably immobilizing fine Ru nanoparticles and increasing the number of Ru active sites that strongly interact with the reduced support, high ammonia synthesis activity is obtained through their synergistic effect.

[0308] exist Figure 2 The image shows Ru / La reduced at different temperatures. 0.5 Ce 0.5 O xHR-TEM and EDX mapping images, and a histogram of Ru particle diameters observed by TEM of the support exposed to air after reduction. In addition, a summary of the results of the characteristics and activity tests of a portion of them is shown in Table 2.

[0309] In addition, as shown in Table 3, even if the reduction temperature is raised from 500°C to 650°C, the average diameter of the Ru particles is approximately the same (1.8 nm or 1.7 nm). However, if the reduction temperature is further raised from 650°C to 800°C, the Ru particle diameter increases from 1.7 nm to 2.7 nm, and the specific surface area decreases from 42 m 2 g -1 decreases to 21 m 2 g -1 .

[0310] Ru dispersion, which is expressed by the ratio of the number of Ru atoms exposed to the surface of the metal support to the total number of Ru atoms contained in the metal support. The Ru dispersion of the metal support shown in Table 3 is calculated from the hydrogen adsorption amount of the Ru-supported metal support. Specifically, assuming that 1 Ru atom adsorbs 1 H atom, the ratio of the number of hydrogen atoms H equivalent to the number of Ru atoms exposed to the surface of the metal support to the total number of Ru atoms Ru supported by the metal support (H / Ru) is denoted as the Ru dispersion. The hydrogen adsorption amount of the metal support can be calculated by the H2 pulse chemisorption method. In the present application, the Ru dispersion based on the hydrogen adsorption amount is denoted as D ads By comparing the metal supports supporting the same amount (the same number of moles) of Ru, it can be found that the higher the Ru dispersion, the greater the number of catalyst active sites.

[0311] As shown in Table 3, D ads (H / Ru) decreases from 0.46 to 0.11 as the reduction temperature is raised from 500°C to 800°C. In the case where the reduction temperature is raised from 500°C to 650°C, D ads decreases from 0.46 to 0.35.

[0312] At this time, if it is assumed that the shape of the Ru particles is a cube, the value of the Ru dispersion can be geometrically calculated using the average particle diameter of Ru (d, unit: nm) calculated by TEM observation, and the calculation method can be expressed by general formula (4). The average particle diameter can be calculated by randomly extracting 100 to 150 points of Ru particles from the TEM image and measuring the particle diameter of each and then calculating the average value thereof. In the present application, the value of the Ru dispersion calculated based on general formula (4) is denoted as D TEM .

[0313] D TEMThe value is 0.62 for reduction at 500℃ and 0.65 for reduction at 650℃, which is higher than the D value calculated using the hydrogen adsorption method. ads The value is larger. For example, under reduction at 650℃, D ads / D TEM =0.54.

[0314] These results indicate that, after reduction at at least 650 °C, approximately 50% of the Ru atoms on the surface of the Ru particles are covered by the support material, i.e., SMSI occurs. It is known that the driving force for SMSI, for example, is Ru / CeO. 2-x The generation of the reduced carrier.

[0315] Table 3 shows the reduction of Ru / La at 500 °C. 0.5 Ce 0.5 O 1.75 The subsequent metal support Ru / La 0.5 Ce 0.5 O x (abbreviated as Ru / La) 0.5 Ce 0.5 O x (500℃), and the metal-supported Ru / La reduced at 650℃ 0.5 Ce 0.5 O x (abbreviated as Ru / La) 0.5 Ce 0.5 O x The relationship between specific surface area and dispersion at 650℃.

[0316] For Ru / La 0.5 Ce 0.5 O 1.75 The reduced metal support, if passed through the reduced Ru / La 0.5 Ce 0.5 O x Based on the oxygen (O2) absorption capacity, Ce is estimated to... 4+ Ce 4+ →Ce 3+ The degree of SMSI reduction was 23% and 43% after reduction at 500℃ and 650℃, respectively. That is, based on this result, it can be seen that the formation of SMSI is strongly correlated with higher temperatures. Furthermore, after reduction at 800℃, SMSI became more pronounced, except for the sintering of Ru particles; this could be significantly reduced to 0.11 by adjusting the H / Ru ratio, and Ce... 4+ The reduction degree increases to 63% as explained. If SMSI is generated in this way, the TOF (catalyst rotation frequency) of Ru increases, from 0.027 s⁻¹ during reduction at 500 °C. -1The values ​​increased to 0.051s during reduction at 650℃. -1 And 0.108s during reduction at 800℃ -1 This is because a portion of the Ru particles contains elements similar to Ce. 4+ Compared to Ce, which is richer in electrons 3+ The reduced support is then covered. The oxygen absorption capacity of the reduced metal support is determined using the following method: The metal support is heated in 60 mL of water for 1 minute. -1 The temperature was increased to 500–800°C under H2 flow and heated at 500°C for 1 hour. The H2 flow was then stopped, and the solution was dispensed in 30 mL / min solution. -1 Ar was passed through the system for 0.5 h. O2 pulse absorption was then measured at room temperature, 450 °C, and 800 °C.

[0317] The Ru metal support used in this invention, when measured by an infrared spectrometer, contains nitrogen molecules adsorbed on Ru particles ( 14 The infrared absorption peak of N2 appears at 2200 cm⁻¹. -1 The following absorption peak originates from the stretching vibration mode of N2 adsorbed on Ru particles by a single N atom, and the absorption region below this frequency indicates a weakened N≡N bond within the nitrogen molecule of the metal support, i.e., it shows a function that promotes the activation of nitrogen molecules.

[0318] In addition, the nitrogen molecules in the Ru metal support used in this invention, derived from those adsorbed on Ru particles ( 14 The infrared absorption peak of N2 appears at 1900–1700 cm⁻¹. -1 This indicates an effect of weakening the N≡N bonds within the nitrogen molecule. Therefore, in the case of catalysts used for activating N≡N bonds in the rate-controlling phase of ammonia synthesis reactions, particularly high activity is observed.

[0319] The infrared absorption peaks are described in detail below. In the metal support of the present invention, the intensity of nitrogen molecules, which is considered as the rate-controlling stage in the synthesis of ammonia from nitrogen and hydrogen, can be investigated by infrared absorption spectroscopy. Nitrogen interacts with the support of the present invention and with the supporting metal. Interaction refers to nitrogen adsorbing onto the metal or undergoing coordination bonding. When nitrogen is in a state of close proximity to the supporting metal along its long axis and interacting with it, the infrared absorption peaks at 2300–2000 cm⁻¹ are observed. -1 ν1 can be observed in this region. This region is where C≡N and C≡C triple bonds can be observed, through... 15 N2 confirms that this vibration is caused by nitrogen molecules used as a raw material. Additionally, nitrogen can also interact with the support, particularly in the low-frequency range of 1900–1500 cm⁻¹. -1Stretching vibrations can also be observed in this region. This region contains functional groups with double bonds such as C=C, C=O, C=N, and N=O. 15 N2 confirmed that the vibration was caused by nitrogen molecules used as a raw material. While not limited by a specific principle, the inventors believe that the empty orbitals of nitrogen molecules receive electrons from the carrier, resulting in a weakened triple bond. In this invention, there are cases where both stretching vibrations ν1 and ν2 are observed, and there are also cases where neither is observed. The N≡N bond can be observed when interacting with the supporting metal. It cannot be observed when interacting with the carrier. Therefore, depending on the exposed area of ​​the metal due to the SMSI effect, velocity theory issues, and the electron-donating properties of the carrier and supporting metal, the observable vibrational frequencies shift, which is the main reason why neither can be observed.

[0320] Regarding Ru / La 0.5 Ce 0.5 O 1.75 To understand the effect of reduction temperature on the activation of N2 molecules, which constitute the rate-controlling stage of ammonia synthesis, the inventors investigated the adsorbed N2 molecules using FT-IR technology. 14 The state of N2. In the case of Ru / La... 0.5 Ce 0.5 O 1.75 The IR spectra of metal supports subjected to reduction treatment at 500℃ and 650℃, after adding N2 at room temperature, are shown in the following figures. Figure 3 The IR spectra of the two catalysts are shown in the figure, at 2164 cm⁻¹. -1 The peak is shown, and it is also located at approximately 1700–1900 cm⁻¹. -1 The peak exhibits a relatively broad width. Notably, as the reduction temperature increases from 500℃ to 650℃, the width of the peak increases from 1883 cm⁻¹. -1 Shift to a lower frequency of 1844cm -1 In the adsorption of 15 In the spectrum under N2 conditions, Ru / La reduced at 500℃ 0.5 Ce 0.5 O x The absorption peak shifts to lower frequencies (2093 cm⁻¹). -1 And 1818cm -1 The peak shifts from the frequency predicted based on isotopic effects (2164 cm⁻¹). -1 ×(14 / 15) 1 / 2 =2091cm -1 and 1885cm -1 ×(14 / 15) 1 / 2 =1821cm -1) are in good agreement. Similarly, for Ru / La 0.5 Ce 0.5 O x , adsorbed 15 N2, the spectra also similarly show that the peaks due to the isotope effect shift to lower frequencies. Thus, all the peaks are due to the stretching vibration mode of N2 adsorbed on a single N atom on the Ru particle. Irrespective of the reduction temperature, the peak appearing at a higher frequency of 2164 cm -1 is due to N2 adsorbed on a Ru atom weakly interacting with the reduced support. On the other hand, the broad peak at 1700 to 1900 cm -1 is due to N2 adsorbed on a Ru atom directly interacting with the reduced support under the action of SMSI. That is, it is known that even after reduction at 500°C, the N≡N bond of N2 is weakened due to the promotion of SMSI.

[0321] From these results, it can be inferred that, in the metal support of the present application, if the frequency of the absorption peak in the infrared absorption spectrum after adsorption of nitrogen 14 N2 on the metal support is 2200 cm -1 or less, the activation of N2 molecules is promoted, and the ammonia synthesis activity of the catalyst is increased. Further, in the case where the catalyst shows an absorption peak at 2200 cm -1 or less, and a characteristic peak at 1900 to 1700 cm -1 , the catalyst has particularly high activity. Further, in the case where the catalyst shows an absorption peak at 2200 cm -1 or less, and a characteristic peak at 1900 to 1700 cm -1 is not observed, and a characteristic peak at 1900 to 1700 cm 0.5 is observed, the catalyst has particularly high activity.

[0322] If the reduction temperature is further increased to more than 650°C, the SMSI phenomenon is intense, and a large amount of electrons moves from the reduced support to the metal Ru, and the N≡N bond on the Ru atom strongly interacting with the reduced support is further weakened. The fact that the ratio of the peak area on the high frequency side to the peak area on the low frequency side decreases as the reduction temperature increases from 500°C to 650°C is in good agreement with the enhancement of SMSI.

[0323] From these results, it can be confirmed that, although the TOF is increased by inducing SMSI by reduction of the metal support at a high temperature, the reduced complex oxide (support) partially covers the Ru surface, and thus the number of active sites of Ru decreases. As a result, after reduction at 650°C, the number of active sites of Ru increases (TOF = 0.051 s -1 , H / Ru = 0.35), and the Ru / La 0.5 Ce0.5 O 1.75 The reduced metal support showed a concentration of 31.3 mmol / g. -1 h -1 Such a high ammonia synthesis rate. On the other hand, after reduction at 800℃, although the activity of the Ru site is very high (TOF = 0.108 s⁻¹),... -1 However, the number of active Ru sites decreased (H / Ru = 0.11). Therefore, the Ru / La ratio was increased at 800℃. 0.5 Ce 0.5 O 1.75 The ammonia synthesis rate of the metal-supported material after reduction treatment is compared with that of Ru / La at 650 °C. 0.5 Ce 0.5 O 1.75 The reduced metal support was smaller, at 21 mmol / g. -1 h -1 For comparison, the specific surface area is only 20 m² when Ru / CeO₂ is reduced at 650℃. 2 g -1 The average diameter of the Ru particles was 2.7 nm, and the H / Ru ratio was 0.17, indicating that the Ru particles were sintered. Conversely, Ru / La was sintered at 650 °C. 0.5 Ce 0.5 O 1.75 Under reduction treatment, calcination was well suppressed, and the catalyst could maintain a high H / Ru ratio.

[0324] <The Effect of Firing Temperature and Reduction Temperature on Ammonia Synthesis Activity>

[0325] As an important element constituting the present invention, the firing temperature of the composite oxide used as a carrier can be cited as an example.

[0326] The catalyst of the present invention is activated by a hydrogen reduction pretreatment at high temperature. This is because not only transition metals such as Ru are reduced, but also cations in the complex oxide (e.g., Ce) are also activated. 4+ The electron-donating ability is also reduced, thus increasing the electron-donating capacity. In addition, the SMSI phenomenon of Ru partially covering the support can be observed at this time.

[0327] Typically, if the pretreatment before reduction is at a high temperature, the sintering of the support will cause an increase in specific surface area and a larger diameter of metal particles, which will lead to a decrease in catalyst activity.

[0328] Take La 0.5 Ce 0.5 O 1.75 Let's take an example to illustrate. Figure 4 Yes, using La at a firing temperature of 600℃ 0.5 Ce0.5 O 1.75 A graph of the ammonia generation rate after reduction at 500°C (Example 69 described below), 650°C (Example 70), 800°C (Example 71) was plotted. From this graph, it was found that with an increase in the reduction temperature, a decrease in the ammonia synthesis activity occurred, and particularly in the case where reduction was performed at 800°C, the ammonia generation rate was greatly decreased.

[0329] Investigation was made on H / Ru, the degree of decrease in the specific surface area, and the change in the Ru particle diameter at this time. The results are shown in Table 1. Figure 5 It was found that when the reduction temperature was increased from 650°C to 800°C, the specific surface area was particularly greatly decreased. It was also found that at this time, the Ru particle diameter was increased, and the calcination of the Ru particle was continuously progressed. H / Ru was also decreased. However, it was considered that this was because the catalyst, which had a low calcination temperature of the support and insufficient structural stability, was subjected to reduction treatment at a high temperature above the calcination temperature of the support.

[0330] That is, it was considered that the reason why the ammonia generation rate was decreased if the reduction temperature was increased was that the specific surface area was decreased due to the enlargement of the support particle by calcination and the continuous progress of the calcination of Ru, and that the appearance of SMSI was excessively progressed due to the instability of the support surface and the Ru particle surface was covered and the number of active sites was decreased.

[0331] On the contrary, in the case where the support calcined at 700°C was used, the ammonia generation rate was higher than that in the case where the support calcined at 600°C was used. 0.5 Ce 0.5 O 1.75 and the activity was measured after reduction at 500°C (Example 1), 650°C (Example 2), 800°C (Example 3) (Table 1). It was found that when the reduction temperature was increased from 500°C to 650°C, a particularly sharp increase in the activity was observed. Referring to Table 1, Figure 4 , since the Ru particle diameter was not changed and H / Ru was decreased, the appearance of the SMSI phenomenon caused the increase in the electron donating property of the support, the electron injection into the antibonding π orbital of N≡N was promoted, and the adsorption and dissociation of N2 as the rate determining stage was promoted. Figure 5

[0332] On the other hand, in the case where reduction was performed at 800°C, although the ammonia generation rate was decreased, the activity was higher than that in the case where the support calcined at 600°C was used and reduction was performed at 800°C. Investigation was made on H / Ru, the degree of decrease in the specific surface area, and the change in the Ru particle diameter at this time.

[0333] ​As a result, it was found that the specific surface area and the Ru particle diameter increase slowly with the increase in reduction temperature, and the Ru aggregation can be suppressed, compared with the case where the support is fired at 600°C. It is considered that this is because the damage caused by the reduction treatment can be reduced by previously firing the support at a higher temperature and stabilizing the structure.

[0334] In particular, in the present composite oxide, the reduction treatment at a high temperature at which the SMSI appears is very important for the catalyst activation, and it is preferable to previously fire the support at a higher temperature than the target reduction treatment temperature.

[0335] By using the Ru-supported metal support of the present application as a catalyst, it is possible to cause the reaction of nitrogen and hydrogen to produce ammonia. The method of synthesizing ammonia itself is not particularly limited, and for example, ammonia can be produced by supplying a raw material gas composed of hydrogen and nitrogen gas in a reaction vessel loaded with the catalyst. The reaction temperature is preferably 300 to 550°C, more preferably 300 to 500°C, and still more preferably 300 to 450°C. The reaction pressure is preferably 0.1 to 20 MPa at low pressure, more preferably 0.1 to 15 MPa, and still more preferably 0.1 to 10 MPa.

[0336] In the case where the Ru-supported metal support of the present application is used as a catalyst, the ammonia generation rate is, for example, 13.4 mmol g -1 h -1 of catalyst per hour at 350°C under 0.1 MPa, or 31.3 mmol g -1 h -1 of catalyst per hour under 1 MPa. This is the same as or higher than the yield obtained by the conventional Ru-based catalyst. The ammonia synthesis reaction generally has a tendency that the higher the pressure, the higher the ammonia yield according to the thermodynamic equilibrium, and therefore, by using the ammonia synthesis catalyst of the present application, it is expected that a higher yield can be obtained under a high pressure condition of, for example, about 10 MPa.

[0337] In the case where the Co-supported metal support of the present application is used as a catalyst, it is preferable that Ba is contained in the composite oxide that becomes the support from the viewpoint of the catalyst activity. By using Co, which is cheaper than Ru, although not as much as the Ru-supported metal support of the present application, a sufficient ammonia synthesis activity can be exhibited based on this combination.

[0338] <Method for producing metal oxide and metal support>

[0339] Next, the method for producing the composite oxide and the metal support of the present application will be described. The composite oxide of the present application can be produced by the following method. The method includes:

[0340] (a) a mixing step of mixing an A precursor containing element A, an X precursor containing element X, and an M precursor containing element M to obtain a mixture;

[0341] (b) a firing step of firing the mixture.

[0342] The metal support of the present application can be further manufactured by a method comprising:

[0343] (c) a supporting step of supporting a compound containing a transition metal on the composite oxide to prepare a reduction treatment pre-support;

[0344] (d) a reduction step of reduction treating the reduction treatment pre-support.

[0345] Hereinafter, the step (a) will be described. The step (a) is a method for manufacturing the composite oxide of the present application. As for the composite oxide, there is a step of mixing an A precursor containing A, an X precursor containing X, and an M precursor containing M as necessary to obtain a mixture (a precursor of the composite oxide).

[0346] The precursor of the composite oxide can be prepared by various methods such as a precipitation method, a complex polymerization method, and the like. For example, a neutralization precipitation method of reacting a precipitant such as ammonia, sodium hydroxide, cesium hydroxide, and the like, with nitrate, chloride, acetate, carbonate, sulfate of A, X, and M to obtain hydroxide can be used.

[0347] Preferably, first, ammonia water and an aqueous nitrate solution are mixed to prepare a composite hydroxide as a precursor of the composite oxide. The mixing molar ratio of ammonia to nitrate is preferably about 5:1 to 2:1, and more preferably about 3:1. The concentrations of ammonia and nitrate in the ammonia water and the aqueous nitrate solution are each preferably about 4 to 32 mol / L and 0.1 to 1 mol / L, respectively, and more preferably about 8 to 16 mol / L and 0.25 to 0.5 mol / L, respectively. The mixing can be performed at normal temperature.

[0348] The precursor of the composite oxide can be obtained by separately preparing products containing one or more of the elements of A, X, and M, and mixing them. Thus, the mixture can be obtained by mixing a compound containing A, a compound containing X, and a compound containing M.

[0349] Next, the step (b) will be described. This step is a step of firing the mixture obtained in the step (a). Thereby, the generated mixture (a precursor of the composite oxide) is changed to a composite oxide having a high specific surface area by firing.

[0350] The firing is preferably performed for about 1 to 10 hours 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, and for about 1 to 10 hours at a high temperature of about 600 to 700°C. The firing temperature of the final step is most preferably 700°C. The firing can be performed in an atmosphere containing oxygen such as air, a mixed gas of an inert gas and oxygen, or the like, and can be performed at an arbitrary oxygen concentration.

[0351] The following describes step (c). In step (c), the composite oxide obtained in step (b) is stirred with a solvent in which a ruthenium supply source is dissolved, so that the ruthenium supply source is impregnated in the composite oxide, and then the solvent is removed by heating and decomposition of the ruthenium supply source after the removal, so that a reduced treatment pre-support in which ruthenium is supported in fine particles on the composite oxide support can be obtained.

[0352] As the ruthenium supply source, various Ru-containing compounds can be used. Preferably, an organometallic compound such as triruthenium dodecacarbonyl, ruthenium acetylacetonate, or the like can be used. A ruthenium supply source other than these, such as ruthenium chloride, ruthenium nitrosyl nitrate, or the like, can also be used.

[0353] In the case where an organometallic compound such as triruthenium dodecacarbonyl is used as the ruthenium supply source, it is advantageous to use an organic solvent as the solvent. As examples of the organic solvent, tetrahydrofuran (THF), alcohol, ethanol, hexane, toluene, or the like can be given. These solvents, if they are commercially available as they are, can be used without special pretreatment, but it is more preferable to use them after refining, dehydration, or the like. The solid component concentration of the composite oxide and the ruthenium supply source, compared with 1 liter of the solvent, is preferably 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. The stirring can be performed at ordinary temperature, and the stirring time is preferably about 1 to 24 hours, and more preferably about 6 to 12 hours. The solvent can be removed by heating using various methods, and it is preferable to perform the heating under a reduced pressure and a low-temperature atmosphere using an evaporator or the like. The decomposition of the ruthenium supply source is performed by heating in an inert atmosphere such as a helium, argon, or nitrogen atmosphere. It can also be performed in an atmosphere containing hydrogen. The heating is performed at a temperature of about 200 to 600°C for about 1 to 12 hours. A more preferable heating temperature is about 300 to 500°C, and a more preferable heating time is about 3 to 6 hours.

[0354] The following describes step (d). Next, the thus obtained support before reduction treatment is subjected to reduction treatment. The purpose of the reduction treatment is to reduce the metal element of IV valence contained in the composite oxide serving as the support, to reduce the transition metal such as Ru, and to perform reduction for the purpose of destroying the carbonate described below. The reduction temperature is from 400°C to 800°C, and is preferably from 600 to 700°C. In the case where the reduction temperature is a high temperature exceeding 500°C, the reduction time is usually from 10 minutes to 40 hours, and is preferably from 30 minutes to 5 hours or so. In the case where the reduction temperature is a low temperature, the reduction time is from 48 hours to 120 hours, and is preferably from 60 hours to 100 hours. The reduction treatment can be performed in the presence of a reducing gas such as hydrogen.

[0355] It is known that, in the case where Ba is contained in a strong alkaline state, BaO reacts with carbon dioxide or the like in the air, and barium carbonate (Ba(C03)) and barium hydroxide (Ba(OH)2) are easily formed. If the carbonate and the hydroxide are formed as such, the partial negative charge of the oxygen of BaO is significantly reduced, and a high alkalinity cannot be obtained. Therefore, in order to exhibit a high ammonia synthesis activity, it is necessary to destroy the carbonate and the hydroxide by an appropriate treatment. For example, as a method of destroying the carbonate Ba to form BaO, a heating treatment (reduction treatment) under a hydrogen stream is effective. This reaction is represented by the following formula.

[0356] BaC03+ 4H2→ BaO + CH4+ 2H20

[0357] By heating the catalyst in a hydrogen atmosphere, dissociation of hydrogen occurs on the surface of the metal species supported, and a hydrogen species having a strong reducing power is generated. Under the action of this hydrogen species, the carbonate Ba is destroyed to become BaO.

[0358] As a method of destroying the carbonate Ba, the catalyst is held under a hydrogen stream at a temperature of 550°C or higher for about 1 hour, and the carbonate Ba can be destroyed. The preferred condition is from 600°C to 800°C or so.

[0359] In addition, by holding the catalyst at a low temperature and under a hydrogen stream for a long time, the carbonate Ba can also be destroyed. The preferred condition is about 48 hours at 500°C, about 72 hours at 450°C, and 120 hours or more at 400°C.

[0360] By using such a method, the carbonate of Ba can be destroyed. In order to exhibit the alkaline property of Ba, it is preferable to reduce the proportion of Ba existing in the form of a carbonate as much as possible. The proportion of Ba existing in the form of a carbonate in the catalyst is preferably 10 mol% or less, more preferably 1 mol% or less, still more preferably 0.1 mol% or less, and particularly preferably 0.01 mol% or less, relative to the entire amount of Ba contained in the catalyst.

[0361] The calcination temperature in the calcination step is most preferably 700 to 800°C. If the calcination temperature in this step is too low, the support and the active metal are excessively calcined during the reduction treatment, the particle diameter becomes large, and thus the number of active sites decreases and the catalyst performance decreases.

[0362] On the other hand, if the calcination temperature in this step is too high, the specific surface area of the support becomes small, and thus the dispersion state of the active metal becomes poor and the particle diameter becomes large, and thus the number of active sites decreases and the catalyst performance decreases.

[0363] As for the relationship between the calcination temperature and the reduction temperature, as described above, the support is preferably calcined at a higher temperature than the reduction treatment temperature from the viewpoint of ammonia synthesis activity.

[0364] The metal support of the present application thus obtained is easy to handle and has good stability in the reaction, as compared with the metal support that has been conventionally used for catalysts for ammonia synthesis.

[0365] For example, in Y. Inoue, M. Kitano, K. Kishida, H. Abe, Y. Niwa, M. Sasase, Y. Fujita, H. Ishikawa, T. Yokoyama, M. Hara, H. Hosono, ACS Catal., (2016) 7577-7584, it is described that Ru / Ca(NH2)2is used as a high-activity catalyst, but it is known that the amide compound as a constituent component easily reacts with moisture and oxygen in the atmosphere. The manufacturing steps are also complicated, and it can be inferred that it is very difficult to handle as an industrial catalyst.

[0366] Note that in the case where Ba or the like is contained in the composite oxide, even if the catalyst is in an oxidized state at the time of manufacture, it easily absorbs CO2to form a carbonate upon exposure to the atmosphere. Therefore, after the carbonate Ba is decomposed by the above-described reduction treatment, until the catalyst is used, it is necessary to be handled so as not to be exposed to CO2, and it is preferable to be stored, for example, by sealing the catalyst in a container filled with an inert gas or the like. In addition, in the case where the support is a carbonate, by hydro-decomposition, it is possible to reduce the carbonate and restore the ammonia synthesis activity.

[0367] In addition, the known oxide-supported ruthenium catalyst, for example, Ru / MgO, in order to improve the ammonia synthesis activity, it is necessary to add an alkali metal such as Cs, which changes to a hydroxide having a melting point in the reaction, and thus it is possible to cause corrosion of the reaction tube (J. G. van Ommen, W. J. Bolink, J. Prasad and P. Mars, J. Catal., 1975, 38, 120-127).

[0368] In addition, there is a report that the active carbon of the support of the Ba-Ru / activated carbon catalyst industrially used in a part of the process is gradually methanated in the reaction and thus the activity is reduced (B. Lin, Y. Guo, J. Lin, J. Ni, J. Lin, L. Jiang, Y. Wang, Appl. Catal., A, 541 (2017) 1-7).

[0369] The metal support loaded in the synthetic reactor for use as a catalyst is inevitably periodically replaced, and since longer time use is envisaged, a metal support that is easy to handle and has excellent stability is required. The metal support of the present application is advantageous in this regard.

[0370] Examples

[0371] Next, the present application is further explained based on examples. Of course, the present application is not limited to these examples.

[0372] Measurement of Ammonia Synthesis Activity

[0373] The measurement of the ammonia synthesis activity of the metal support was performed using a fixed bed flow type reaction apparatus. The metal support subjected to the pretreatment using the method described in the examples and comparative examples was left to cool to 300°C while flowing Ar. The temperature of the metal support layer was maintained at 300°C, and the pressure was increased to 1.0 MPa or 3.0 MPa by a back pressure valve at the outlet of the reaction tube while supplying Ar. The supply of Ar was stopped, the pressure was maintained, and 200 mL of a 1 to 100 mM (1, 5, 10, 25, 100 mM) aqueous sulfuric acid solution was added to a three-necked flask connected to a conductivity meter, and the mixed gas containing hydrogen (purity 99.995%, Fukuoka Oxygen Manufacturing), nitrogen (purity 99.995%, Fukuoka Oxygen Manufacturing), NH3, which flowed out from the outlet of the reaction tube, was bubbled in the aqueous sulfuric acid solution. In addition, a gas purifier (gas purification filter MC50-904F, manufactured by SAES) was used in the case where impurities such as water and oxygen were removed, and the purity was made to be 99.99999999 or more. At this time, the amount of ammonia generated in the outlet gas was quantified by measuring the change in the conductivity due to the reaction of NH3with sulfuric acid. Next, the temperature of the metal support layer was increased to 350°C or 400°C. After the temperature of the metal support layer was stabilized at 350°C or 400°C, it was left for 10 minutes, and the amount of ammonia generated was quantified using the same method as described above. -1 and 30 mLmin -1 (space velocity 72 Lh -1 g -1 )H2and N2were flowed, and the reaction atmosphere was switched. Depending on the degree of NH3synthesis activity, 200 mL of a 1 to 100 mM (1, 5, 10, 25, 100 mM) aqueous sulfuric acid solution was added to a three-necked flask connected to a conductivity meter, and the mixed gas containing hydrogen (purity 99.995%, Fukuoka Oxygen Manufacturing), nitrogen (purity 99.995%, Fukuoka Oxygen Manufacturing), NH3, which flowed out from the outlet of the reaction tube, was bubbled in the aqueous sulfuric acid solution. In addition, a gas purifier (gas purification filter MC50-904F, manufactured by SAES) was used in the case where impurities such as water and oxygen were removed, and the purity was made to be 99.99999999 or more. At this time, the amount of ammonia generated in the outlet gas was quantified by measuring the change in the conductivity due to the reaction of NH3with sulfuric acid. Next, the temperature of the metal support layer was increased to 350°C or 400°C. After the temperature of the metal support layer was stabilized at 350°C or 400°C, it was left for 10 minutes, and the amount of ammonia generated was quantified using the same method as described above.

[0374] <Measurement of powder X-ray diffraction>

[0375] The powder X-ray diffraction pattern of the metal support (catalyst) was measured by a SmartLab x-ray diffractometer (Rigaku Corporation).

[0376] <Measurement of specific surface area>

[0377] The specific surface area of the metal support was measured by the BET method based on the amount of nitrogen adsorption at 77 K using a BEL-sorp mini (BEL Japan). Prior to the measurement, vacuum heating at 300°C was performed for 2 hours as a pretreatment.

[0378] <Measurement of infrared absorption spectrum>

[0379] The infrared absorption spectrum was measured using a rapid Fourier transform type infrared spectrophotometer (FT / IR-6600, JASCO). In a glass cuvette into which H2 at 80 kPa was enclosed, a catalyst molded into a disc shape with a diameter of 10 mm was placed, and heated to 500°C while circulating H2. After being left to cool to room temperature, the cuvette was evacuated to vacuum, and the infrared absorption spectrum was measured and used as a background. Thereafter, N2 at 8 kPa was introduced and adsorbed to the catalyst, and the infrared absorption spectrum was measured, and a difference spectrum from the background was obtained. 14 15 -1 -1

[0380] <Observation of transmission electron microscope image>

[0381] A high-angle annular dark-field scanning type transmission electron microscope (HAADF-STEM) image and a high-resolution scanning type transmission electron microscope (HR-STEM) image were obtained by a JEM-ARM200F atomic resolution microscope (JEOL). The sample for observation was prepared by crushing the product after hydrogen reduction of the metal support at 500°C or 650°C in the atmosphere, dispersing it in an ethanol aqueous solution, dropping it on a grid made of copper, and drying.

[0382] <Measurement of Ru dispersibility>

[0383] The Ru dispersibility of the metal support was obtained by a H2 pulse chemisorption method. The metal support was heated to 500 to 800°C under the flow of H2 at 60 mL min -1 for 1 h to perform reduction treatment. The flow of H2 was stopped, and Ar was flowed at 30 mL min -1 for 0.5 h. Thereafter, it was cooled to -74°C, and a prescribed amount of H2 was supplied in a pulse form, and the amount of decrease in hydrogen due to adsorption of the metal support was measured.

[0384] <Determination of Catalyst Reduction Capacity>

[0385] The reduction capacity of the catalyst was determined based on the O2 pulse absorption. The catalyst was then subjected to a 60 mL / min... -1 The temperature was increased to 500–800°C under H2 flow and heated at 500°C for 1 hour. The H2 flow was then stopped, and the solution was dispensed in 30 mL / min solution. -1 Ar flow was carried out for 0.5 h. Afterwards, a predetermined amount of O2 was supplied in a pulsed manner at room temperature, 450 °C, and 800 °C, respectively. The amount of O2 absorbed due to catalyst oxidation, i.e., the amount of O2 consumed in the oxidation of metallic Ru to RuO2, and Ce... 3+ Oxidized to Ce 4+ The amount of O2 required at that time. It should be noted that this assumes Ru in its metallic state is oxidized to RuO2, and the amount of O2 consumed by the oxidation of Ru is subtracted from the amount of O2 absorbed by the composite oxide of the support. By calculating this O2 absorption, Ce can be determined. 4+ The degree of reduction (i.e., with Ce) 3+ (proportion).

[0386] It should be noted that, using the same method, we can find the Pr of elements other than Ce that can undergo +3 and +4 valence changes, such as Pr and Tb. 4+ 、Tb 4+ The degree of restoration.

[0387] <Partial negative charge of oxygen>

[0388] The partial negative charge of oxygen contained in the composite oxide (support) was calculated. First, the composition ratio of all elements other than oxygen (Mg, Ba, Zr, La, Ce, Pr) in the support was determined, ensuring that the total composition of these elements equals 1. For example, in Ru / Ba... 0.1 La 0.45 Ce 0.45 O x In this case, the composition ratio of each element is Ba = 0.1, La = 0.45, and Ce = 0.45. Oxygen is considered to be O = 1.675 (Ba is in oxidation state II, La is in oxidation state III, and Ce is between oxidation state III in a completely reduced state and oxidation state IV in a completely oxidized state). This value is denoted as ni (i = Mg, Ba, Zr, La, Ce, Pr, O).

[0389] Next, the electronegativity χi values ​​for each element (Mg, Ba, Zr, La, Ce, Pr, C, O) were determined. The electronegativity values ​​were obtained from Tables 6 and 7 on page 122 of Sanderson's Inorganic Chemistry (Volume 1) published by Hirokawa Shoten (1967). (This electronegativity is referred to as the "Sanderson electronegativity".)

[0390] Next, the geometric mean of the electronegativity is calculated. It is calculated by the formula (Π (χi^ni))^(1 / (∑ni)).

[0391] Next, the change in the electronegativity of oxygen in the carrier is calculated. The change is calculated using the difference between the geometric mean of the electronegativity of the complex oxide and the electronegativity of oxygen (5.21). Note that the geometric mean of the electronegativity varies depending on the change in the composition of the oxide accompanying the change in the valence of the atom. Therefore, for a metal oxide containing a valence-variable element such as Pr or Ce, the calculation method needs to be changed in the case where the proportion of the element contained in each valence can be quantified and in the case where it cannot be quantified. Specifically, in the case where the proportion of the element contained in each valence can be quantified, the electronegativity is calculated from the proportion. On the other hand, in the case where the proportion of the element contained in each valence of the valence-variable element cannot be quantified, the case where the element is completely oxidized and the case where it is completely reduced are calculated independently. Further, in the case where Ba, which is a strong base, is contained, the possibility that Ba reacts with carbon dioxide in the atmosphere to form BaCO3 is assumed, and this is regarded as a case where the partial negative charge of oxygen is originally small.

[0392] Finally, the partial negative charge "-δ O " of the carrier oxygen is calculated. This is the change in the electronegativity of oxygen divided by the value "-4.75". This -4.75 is the change in the electronegativity in the case where one oxygen atom acquires one electron, and the value is selected from Table 6 and Table 7 in Sanderson "Inorganic Chemistry (I)" described above. In the case where the proportion of the element contained in each valence of the valence-variable element cannot be quantified, the numerical value has a range, and a smaller numerical value indicates a case where the element is not reduced at all, and a larger numerical value indicates a case where the element is completely reduced. O corresponds to the partial negative charge of the carrier oxygen. It can be found that this value is correlated with the NH3 synthesis activity of the catalyst.

[0393] (Example 1)

[0394] < Ru / Ce 0.5 La 0.5 O x _500°C reduction

[0395] <Preparation of complex oxide>

[0396] Ce 0.5 La 0.5 O xThe composite oxide was synthesized using a reverse heterogeneous precipitation method as follows. La(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water (Takugaku Pharmaceutical) to form an aqueous La(N03)3solution. Ce(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Ce(N03)3solution. The aqueous La(N03)3solution and the aqueous Ce(N03)3solution were mixed to prepare a 250 mL support precursor solution containing a total of 0.0625 mol of La and Ce. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added to a 1000 mL beaker in 250 mL, while stirring with a magnetic stirrer at 320 rpm, the above support precursor solution was added all at once, and stirring was continued for 1 hour. After standing for 30 minutes, 350 mL of supernatant was removed, and after adding 350 mL of ion exchange water, stirring was performed for 30 minutes. This series of operations was performed four times, the precipitate was filtered, and the dried precipitate was pulverized with a mortar. The obtained powder was heated at 700°C for 5 hours under an atmospheric atmosphere using an electric furnace, thereby obtaining Ce 0.5 La 0.5 O 1.75 .

[0397] <Ru loading>

[0398] Ru was loaded on Ce 0.5 La 0.5 O x by an impregnation method. A tetrahydrofuran (THF) (Wako Pure Chemical Industries) solution in which Ru3(CO) 12 (a transition metal) as a Ru precursor was dissolved was prepared in a 200 mL Erlenmeyer flask, 5 g of the support was added thereto, and stirring was performed for 18 hours or more. Note that the amount of Ru3(CO) 12 and the support used was appropriately adjusted so that the amount of Ru contained in the catalyst after heating under an argon atmosphere was 5% by weight. After the stirred suspension was subjected to reduced pressure drying at 35°C under 0.3 atm using a rotary evaporator, the obtained powder was dried at 80°C for 18 hours using a furnace. The obtained powder was heated at 500°C for 5 hours under an argon gas flow of 25 mL / min -1 using a tubular electric furnace, thereby removing the carbonyl ligand in the precursor. By the above operations, a Ru / Ce 0.5 La 0.5 O x metal loading was obtained.

[0399] <hydrogen reduction pretreatment>

[0400] The Ru / Ce 0.5 La 0.5 O 1.75, a part of Ce is changed to III valence by hydrogen reduction pretreatment (referred to as "pretreatment" hereinafter) by the following method. The powder of the metal support is pressed at 20 MPa for 5 min to make a disc, the disc is crushed with a mortar, and classification is performed using a sieve to make pellets. The size of the pellets is adjusted to 250 to 500 μm in diameter. 100 mg of the pellets is filled in a catalyst reaction tube made of Inconel (trademark) having a diameter of 7 mm, and the catalyst layer is fixed before and after using quartz wool. The reaction tube is set in a fixed bed flow type reaction apparatus for ammonia synthesis activity measurement, and 60 mL min -1 of H2is circulated in the reaction tube filled with the pellets, and heated at 500°C for 1 h to obtain Ru / Ce 0.5 La 0.5 O x reduced at 500°C.

[0401] (Example 2)

[0402] <Ru / Ce 0.5 La 0.5 O x reduced at 650°C.

[0403] The same operation as in Example 1 was performed except that the holding temperature of the pretreatment in Example 1 was set to 650°C to obtain Ru / Ce 0.5 La 0.5 O x reduced at 650°C.

[0404] (Example 3)

[0405] <Ru / Ce 0.5 La 0.5 O x reduced at 800°C.

[0406] The same operation as in Example 1 was performed except that the holding temperature of the pretreatment in Example 1 was set to 800°C to obtain Ru / Ce 0.5 La 0.5 O x reduced at 800°C.

[0407] (Example 4)

[0408] <Ru / Ce 0.5 Zr 0.5 O x reduced at 700°C.

[0409] <Composite Oxide>

[0410] Ce 0.5 Zr 0.5 O x, using reverse heterogeneous precipitation method as follows. ZrO(N03)2-2H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous ZrO(N03)2solution. Ce(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Ce(N03)3solution. The aqueous La(N03)3solution was mixed with the aqueous Ce(N03)3solution to prepare a support precursor solution of 300 mL containing 0.15 mol of Zr and Ce in total. To 300 mL of 28% aqueous NH3(Wako Pure Chemical Industries) in a 1000 mL beaker, the above support precursor solution was added dropwise at a rate of 2 mL per minute using a pump while stirring at 320 rpm using a magnetic stirrer, and stirring was continued for 18 hours. After that, the mixture was left to stand for 1 hour and filtered. To the slurry remaining on the filter paper, 800 mL of ion exchange water was added, stirred for 2 h, and left to stand for 1 hour. This was repeated three times, and the obtained slurry was dried at 80°C for 15 hours using a furnace. After that, the dried powder was heated at 700°C for 5 hours under an atmospheric atmosphere to obtain Ce 0.5 Zr 0.5 O2.

[0411] <Loading of Ru>

[0412] As for the loading of Ru, by the same operation as in Example 1, Ru / Ce 0.5 Zr 0.5 O2metallic support.

[0413] <Pre-treatment by hydrogen reduction>

[0414] The same operation as in Example 1 was performed except that the holding temperature in Example 1 was set to 700°C to obtain Ru / Ce 0.5 Zr 0.5 O 1.75 700°C reduction.

[0415] (Example 5)

[0416] <Loading of Ru / Pr 0.5 La 0.5 O x 600°C reduction>

[0417] <Composite oxide>

[0418] Pr 0.5 La 0.5 O 1.675, were synthesized as follows using the reverse homogeneous precipitation method. La(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous La(N03)3solution. Pr(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Pr(N03)3solution. The aqueous La(N03)3solution and the aqueous Pr(N03)3solution were mixed to prepare a 250 mL support precursor solution containing a total of 0.0625 mol of La and Pr. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added 250 mL in a 1000 mL beaker while stirring with a magnetic stirrer at 320 rpm, and the above support precursor solution was added all at once, and stirring was continued for 11 h. After standing for 30 minutes, 350 mL of supernatant was removed, and after adding 350 mL of ion exchange water, stirring was performed 6 times for 30 minutes, the precipitate was filtered, and dried at 80°C for 15 hours using a furnace. The dried precipitate was pulverized with a mortar, and the resulting powder was heated at 700°C for 5 hours under an atmospheric atmosphere using an electric furnace, thereby obtaining Pr 0.5 La 0.5 O 1.675 .

[0419] <Ru loading>

[0420] As for the loading of Ru, by the same method as in Example 1, Ru / Pr 0.5 La 0.5 O x metal load.

[0421] <hydrogen reduction pretreatment>

[0422] By the same operation as in Example 1 except that the holding temperature of the pretreatment in Example 1 was set to 600°C, Ru / Pr 0.5 La 0.5 O x 800°C reduction.

[0423] (Example 6)

[0424] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x 650°C reduction>

[0425] <composite oxide preparation>

[0426] Ba 0.1 La 0.45 Ce 0.45 O 1.675, using a reverse heterogeneous precipitation method as follows. La(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous La(N03)3solution. Ce(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Ce(N03)3solution. Ba(N03)2-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Ba(N03)2solution. The aqueous La(N03)3solution and the aqueous Ce(N03)3solution were mixed, and the aqueous Ba(N03)2solution was mixed to prepare a 250 mL support precursor solution containing a total of 0.0625 mol of La and Ce and Ba. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added 250 mL in a 1000 mL beaker, while stirring with a magnetic stirrer at 320 rpm, the above support precursor solution was added all at once, and stirring was continued for 1 hour. After that, it was left standing for 12 hours, and the precipitate (1) was separated by suction filtration. The separated filtrate was recovered in a 2 L beaker. To the separated precipitate (1), 350 mL of ion exchange water was added, stirring was performed for 30 minutes and the precipitate was washed, and the precipitate (1) was separated by suction filtration. This washing operation was performed 3 times. The ion exchange water used in the washing was all recovered, and the filtrate and the washings were added to a 2 L beaker and mixed, and the mixed solution was left standing for 12 hours, so that a white precipitate (2) was produced, and the produced precipitate (2) was recovered by suction filtration. The precipitate (1) and the precipitate (2) were mixed, and the dried precipitate was pulverized with a mortar, and the obtained powder was heated at 700°C for 5 hours under an atmospheric atmosphere using an electric furnace, whereby Ba 0.1 La 0.45 Ce 0.45 O 1.675 .

[0427] <Loading of Ru>

[0428] As for the loading of Ru, by the same operation as in Example 1, Ru / Ba 0.1 La 0.45 Ce 0.45 O x metal carrier.

[0429] <Pre-treatment by hydrogen reduction>

[0430] By the same operation as in Example 1 except that the holding temperature of the pre-treatment in Example 1 was set to 650°C, Ru / Ba 0.1 La 0.45 Ce 0.45 O x _650°C reduction.

[0431] (Example 7)

[0432] <Ru / Ba 0.1 Pr 0.45 Ce 0.45 O x 650°C reduction

[0433] <Preparation of composite oxide>

[0434] Except for dissolving Pr(NO3)3-6H2O (Wako Pure Chemical Industries) in purified water and using it as an aqueous Pr(NO3)3 solution instead of the aqueous La(NO3)3 solution used in Example 6, the aqueous solutions were mixed in the same manner as in Example 6. Then, a carrier precursor solution of 250 mL containing a total of 0.0625 mol of Pr and Ce and Ba was prepared, and the same operations were further performed to obtain Ba 0.1 Pr 0.45 Ce 0.45 O 1.9 .

[0435] <Ru loading>

[0436] With respect to the loading of Ru, Ru / Ba 0.1 Pr 0.45 Ce 0.45 O 1.9 metal carrier was obtained by the same operations as in Example 1.

[0437] <Pre-treatment by hydrogen reduction>

[0438] Except for setting the holding temperature of the pre-treatment in Example 1 to 650°C, Ru / Ba 0.1 Pr 0.45 Ce 0.45 O x 650°C reduction.

[0439] (Example 8)

[0440] <Ru / Ba 0.3 Pr 0.35 Ce 0.35 O x 650°C reduction

[0441] <Preparation of composite oxide>

[0442] Except for preparing a carrier precursor solution of 250 mL containing a total of 0.0625 mol of Pr and Ce and Ba, Ru / Ba 0.3 Pr 0.35 Ce 0.35 O 1.7 .

[0443] <Loading of Ru>

[0444] As for the loading of Ru, the same operation as in Example 1 was performed to obtain Ru / Ba 0.3 Pr 0.35 Ce 0.35 O 1.7 metallic carrier.

[0445] <Pre-treatment by hydrogen reduction>

[0446] Except that the holding temperature of the pre-treatment in Example 1 was set to 650°C, the same operation as in Example 1 was performed to obtain Ru / Ba 0.3 Pr 0.35 Ce 0.35 O x reduction at 650°C.

[0447] (Example 9)

[0448] <Loading of Ru / La 0.5 Pr 0.5 O x reduction at 650°C>

[0449] <Preparation of composite oxide>

[0450] Except that Pr(NO3)3-6H2O (Wako Pure Chemical Industries) was dissolved in purified water instead of the Ce(NO3)3 aqueous solution used in Example 1 and used as an aqueous Pr(NO3)3 solution, the aqueous solutions were mixed in the same manner as in Example 1. Then, a carrier precursor solution of 250 mL containing a total of 0.0625 mol of La and Pr was prepared, and the same operation was further performed to obtain La 0.5 Pr 0.5 O 1.75 .

[0451] <Loading of Ru>

[0452] As for the loading of Ru, the same operation as in Example 1 was performed to obtain Ru / La 0.5 Pr 0.5 O 1.75 metallic carrier.

[0453] <Pre-treatment by hydrogen reduction>

[0454] Except that the holding temperature of the pre-treatment in Example 1 was set to 650°C, the same operation as in Example 1 was performed to obtain Ru / La 0.5 Pr 0.5 O x reduction at 650°C.

[0455] (Example 10)

[0456] <Co / Ba 0.3 Ce 0.35 Pr 0.35 O x _650℃ reduction>

[0457] <Preparation of composite oxides>

[0458] Except that Pr(NO3)3·6H2O (Wako Pure Chemical Industries Co., Ltd.) was dissolved in purified water and used as the Pr(NO3)3 aqueous solution instead of the La(NO3)3 aqueous solution used in Example 6, the aqueous solution was mixed in the same manner as in Example 6. Then, 250 mL of a carrier precursor solution containing a total of 0.0625 mol of Pr, Ce, and Ba was prepared, and the same operation was performed again to obtain Ba. 0.3 Ce 0.35 Pr 0.35 O 1.7 .

[0459] <Co's Load>

[0460] Co loading was performed by evaporation-drying. Co(NO3)2·6H2O (Wako Pure Chemicals) was used as the Co precursor and dissolved in purified water to prepare a 250 mL aqueous solution. Ba was then added to the solution. 0.3 Ce 0.35 Pr 0.35 O x After stirring for 12 hours, the aqueous solution was heated and stirred with a hot stirrer to remove moisture. It should be noted that the amounts of Co(NO3)2·6H2O and the support were appropriately adjusted so that the amount of Co in the catalyst after heating in air was 10% by weight. The dried powder was recovered and dried in a dryer at 70°C for 12 hours. Afterwards, it was heated in 300 mL of water for 1 minute. -1 Under air circulation, the solution is kept at 500°C for 5 hours to remove nitrates, yielding Co / Ba. 0.3 Ce 0.35 Pr 0.35 O 1.7 .

[0461] <Pretreatment for Hydrogen Reduction>

[0462] Except that the pretreatment holding temperature in Example 1 was set to 650°C, Co / Ba was obtained through the same operation as in Example 1. 0.3 Ce 0.35 Pr 0.35 O x Reduced at 650℃.

[0463] (Example 11)

[0464] <Co / Ba0.3 Ce 0.35 Pr 0.35 O x 650°C reduction

[0465] Except for using twice the amount of Co precursor as in Example 10, Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 500°C reduction.

[0466] (Example 12)

[0467] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 500°C reduction.

[0468] Hydrogen reduction pretreatment

[0469] Except for setting the holding temperature of the pretreatment in Example 10 to 500°C, Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 500°C reduction.

[0470] (Example 13)

[0471] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 600°C reduction.

[0472] Hydrogen reduction pretreatment

[0473] Except for setting the holding temperature of the pretreatment in Example 10 to 600°C, Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 600°C reduction.

[0474] (Example 14)

[0475] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 700°C reduction.

[0476] Hydrogen reduction pretreatment

[0477] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 700°C.

[0478] (Example 15)

[0479] < Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 750°C.

[0480] < Hydrogen reduction pretreatment >

[0481] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 750°C.

[0482] (Example 17)

[0483] < Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 700°C.

[0484] < Preparation of composite oxide • hydrogen reduction pretreatment >

[0485] Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 700°C.

[0486] (Example 18)

[0487] < Co / Ba 0.3 Ce 0.35 Pr 0.35 O x reduction at 650°C.

[0488] < Hydrogen reduction pretreatment >

[0489] Co / Ba0.3 Ce 0.35 Pr 0.35 O x 650°C reduction.

[0490] (Example 19)

[0491] <Co / Ba 0.3 La 0.35 Pr 0.35 O x 650°C reduction.

[0492] <hydrogen reduction pretreatment>

[0493] Except for substituting La(N03)3-6H20 (Wako Pure Chemical Industries) for the Ce(N03)3 aqueous solution used in Example 10, dissolving the Co precursor in a double amount, and setting the holding temperature of the pretreatment to 650°C, Co / Ba 0.3 Ce 0.35 Pr 0.35 O x 650°C reduction.

[0494] (Example 20)

[0495] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x 500°C reduction.

[0496] <compounding of composite oxides>

[0497] La(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous La(N03)3solution. Ce(N03)3-6H20 (Showa Denko) was dissolved in purified water to form an aqueous Ce(N03)3solution. The aqueous La(N03)3solution and the aqueous Ce(N03)3solution were mixed to prepare a 250 mL support precursor solution containing a total of 0.0625 mol of La and Ce. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added to a 1000 mL beaker in 250 mL, while stirring with a magnetic stirrer at 320 rpm, the above support precursor solution was added all at once, and stirred for 1 hour. After standing for 30 minutes, 350 mL of supernatant was removed, and after adding 350 mL of ion exchange water, stirring was performed for 4 times for 30 minutes, and the precipitate was filtered. Ba(OH)2(Wako Pure Chemical Industries) was dissolved in purified water to form an aqueous Ba(OH)2solution. The precipitate was added to the aqueous Ba(OH)2solution, and stirred for 5 minutes using a magnetic stirrer. The stirred suspension was subjected to reduced pressure drying using a rotary evaporator at 35°C under 0.3 atm, and then dried using a furnace at 80°C for 15 hours. The dried precipitate was pulverized using a mortar, and the obtained powder was heated at 700°C under an atmospheric atmosphere for 5 hours, thereby obtaining Ba 0.1 La 0.45 Ce 0.45 O 1.675 .

[0498] <Ru loading>

[0499] As for the Ru loading, by the same operation as in Example 6, Ru / Ba 0.1 La 0.45 Ce 0.45 O 1.675 metal support was obtained.

[0500] <hydrogen reduction pretreatment>

[0501] By the same operation as in Example 6, except that the holding temperature of the pretreatment in Example 6 was set to 500°C, Ru / Ba 0.1 La 0.45 Ce 0.45 O x 500°C reduction.

[0502] (Example 21)

[0503] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x 600°C reduction>

[0504] <hydrogen reduction pretreatment>

[0505] Except that the holding temperature of the pretreatment in Example 20 was set to 600°C, Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 600°C.

[0506] (Example 22)

[0507] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 650°C.

[0508] <hydrogen reduction pretreatment>

[0509] Except that the holding temperature of the pretreatment in Example 20 was set to 650°C, Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 650°C.

[0510] (Example 23)

[0511] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 700°C.

[0512] <hydrogen reduction pretreatment>

[0513] Except that the holding temperature of the pretreatment in Example 20 was set to 700°C, Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 700°C.

[0514] (Example 24)

[0515] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x reduction at 750°C.

[0516] <hydrogen reduction pretreatment>

[0517] Except that the holding temperature of the pretreatment in Example 20 was set to 750°C, Ru / Ba 0.1 La0.45 Ce 0.45 O x _ 750°C reduction

[0518] (Comparative Example 1)

[0519] Ru / Ce 0.9 La 0.1 O x _ 450°C reduction

[0520] As a comparative example, a catalyst was prepared by the method described in Non-Patent Literature 2. Specifically, first, RuCl3 / 3H2O, Ce(NO3)3 / 6H2O, La(NO3)3 / 6H2O were dissolved in an aqueous solution to prepare a mixed aqueous solution of a total of 300 mL. Hydrogen peroxide water was added thereto and mixed so that the molar ratio of H2O2 to Ce 3+ was 1:3. This mixed aqueous solution was stirred for 30 minutes while maintaining 60°C, and an aqueous solution of KOH was gradually added so that a precipitate was precipitated, and then stirred for another 60 minutes. Thereafter, the mixed solution containing the precipitate was cooled to room temperature until the precipitate was separated by centrifugal separation. The precipitate after separation was washed with ion exchange water and dried at 120°C for 24 hours. Except that 45 mL min -1 of H2and 15 mL min -1 of N2were simultaneously flowed through the reaction tube during pretreatment, and the holding temperature was set to 450°C, Ru / Ce 0.9 La 0.1 O x _ 450°C reduction

[0521] (Comparative Example 2)

[0522] Ru / Ce 0.9 La 0.1 O x _ 500°C reduction

[0523] Except that the holding temperature of the pretreatment in Comparative 1 was set to 500°C, Ru / Ce 0.9 La 0.1 O x _ 500°C reduction

[0524] The metal supports obtained in each of the examples and comparative examples were investigated for ammonia synthesis activity. The results are shown in Tables 2 to 3. In addition, the results of measuring the physical properties of each of the composite oxides are shown in Table 4. Note that in the case where "O" is indicated in the table with respect to the use of a gas purifier, the reaction gas was treated in advance using a gas purifying filter (MC50-904F) manufactured by SAES Corporation, and the impurities such as H2O and O2 were reduced to less than 100 ppt, and then supplied.

[0525] [Table 2]

[0526]

[0527] [Table 3]

[0528]

[0529] [Table 4]

[0530]

[0531] According to the results, it was found that the comparative examples in which the calcination was not performed at a high temperature and the proportion of the trivalent Ce was small had poor ammonia synthesis activity (ammonia yield and ammonia generation rate).

[0532] Note that the proportion of the trivalent Ce in the catalysts of Comparative Examples 1 and 2 prepared by the method described in Non-Patent Literature 2 was 5% and 7%, respectively, as determined from the amount of reduction of the catalyst. Note that although the proportion of the trivalent Ce in the composite oxide was determined by X-ray photoelectron spectroscopy in Non-Patent Literature 2, X-ray photoelectron spectroscopy can analyze only the very surface of several atomic layers or less to which X-rays can be irradiated, in principle. Generally, reduction of a catalyst is mainly performed from the vicinity of the surface of the catalyst particles, due to the problem of contact with a reducing agent (for example, hydrogen gas used in the present application). Therefore, it is considered that the values described in Non-Patent Literature 2 evaluate only the proportion of the trivalent Ce at the surface, and the proportion of the trivalent Ce is considered to be excessive when the catalyst as a whole is considered.

[0533] (Example 25)

[0534] <Ru / Ba 0.1 La 0.45 Ce 0.45 O x _800°C reduction

[0535] Ru / Ba 0.1 La0.45 Ce 0.45 O x 800°C reduction.

[0536] (Example 26)

[0537] Ru / Ba 0.05 La 0.475 Ce 0.475 O x 700°C reduction.

[0538] Except that the Ba precursor in Example 20 was selected in an amount of half, by the same operation as Example 20, Ru / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0539] (Example 27)

[0540] Ru / Ba 0.15 La 0.42.5 Ce 0.425 O x 700°C reduction.

[0541] Except that the Ba precursor in Example 20 was selected in an amount of 1.5 times, by the same operation as Example 20, Ru / Ba 0.15 La 0.42.5 Ce 0.425 O x 700°C.

[0542] (Example 28)

[0543] 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction.

[0544] Preparation of catalyst

[0545] Ru / Ce 0.5 La 0.5 O x After that, using Ba(N03)2-6H20 as a raw material, Ba was supported by an evaporation drying method in an amount of 10 mol% with respect to Ru. Further, except that the holding temperature of the pretreatment was set to 700°C, the same operation as Example 1 was performed, and 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction.

[0546] < Hydrogen reduction pretreatment >

[0547] The same operation as in Example 1 was performed except that the holding temperature of the pretreatment in Example 1 was set to 700°C, to obtain 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction.

[0548] (Example 29)

[0549] <10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 500°C reduction

[0550] The same operation as in Example 28 was performed except that Ba(NO3)2-6H2O was not used but Ba(OH)2was used as a raw material in Example 28, and the holding temperature of the pretreatment was set to 500°C, to obtain 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 500°C reduction.

[0551] (Example 30)

[0552] <10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 650°C reduction

[0553] The same operation as in Example 29 was performed except that the holding temperature of the pretreatment in Example 29 was set to 650°C, to obtain 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 650°C reduction.

[0554] (Example 31)

[0555] <10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction

[0556] The same operation as in Example 29 was performed except that the holding temperature of the pretreatment in Example 29 was set to 700°C, to obtain 10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction.

[0557] (Example 32)

[0558] <10 mol% Ba / Ru / La 0.5 Ce 0.5 O x 800°C reduction

[0559] Except that the holding temperature of the pre-treatment in Example 29 was set to 800°C, 10 mol% Ba / Ru / La was obtained by the same operation as in Example 29. 0.5 Ce 0.5 O x 800°C reduction.

[0560] (Example 33)

[0561] <5 mol% Ba / Ru / La 0.5 Ce 0.5 O x 450°C reduction

[0562] Except that the Ba precursor in Example 29 was selected in half the amount, and the holding temperature of the pre-treatment was set to 450°C, 5 mol% Ba / Ru / La was obtained by the same operation as in Example 29. 0.5 Ce 0.5 O x 450°C reduction.

[0563] (Example 34)

[0564] <5 mol% Ba / Ru / La 0.5 Ce 0.5 O x 650°C reduction

[0565] Except that the holding temperature of the pre-treatment in Example 33 was set to 650°C, 5 mol% Ba / Ru / La was obtained by the same operation as in Example 33. 0.5 Ce 0.5 O x 650°C reduction.

[0566] (Example 35)

[0567] <5 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction

[0568] Except that the holding temperature of the pre-treatment in Example 33 was set to 700°C, 5 mol% Ba / Ru / La was obtained by the same operation as in Example 33. 0.5 Ce 0.5 O x 700°C reduction.

[0569] (Example 36)

[0570] <5 mol% Ba / Ru / La 0.5 Ce 0.5 O x 800°C reduction

[0571] Except that the holding temperature of the pre-treatment in Example 33 was set to 800°C, 5 mol% Ba / Ru / La 0.5 Ce 0.5 O x 800°C reduction.

[0572] (Example 37)

[0573] <1 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction

[0574] Except that the Ba precursor in Example 29 was selected in an amount of 1 / 10, and the holding temperature of the pre-treatment was set to 700°C, 1 mol% Ba / Ru / La 0.5 Ce 0.5 O x 700°C reduction.

[0575] (Example 39)

[0576] <Ru / Ba 0.1 La 0.9 O x 700°C reduction

[0577] Except that in Example 1, instead of the raw material Ce(N03)3-6H20, Ba(N03)2-6H20 was used, and the holding temperature of the pre-treatment was set to 700°C, Ru / Ba 0.1 La 0.9 O x 700°C reduction.

[0578] (Example 40)

[0579] <Ru / Ba 0.1 La 0.9 O x 500°C reduction

[0580] Except that the holding temperature of the pre-treatment in Example 39 was set to 500°C, Ru / Ba 0.1 La 0.9O x 500°C reduction.

[0581] (Example 41)

[0582] Ru / Ba 0.1 La 0.9 O x 800°C reduction

[0583] Except that the holding temperature of the pretreatment in Example 39 was set to 800°C, Ru / Ba 0.1 La 0.9 O x 800°C reduction.

[0584] (Example 42)

[0585] Ru / Ba 0.1 La 0.9 O x 900°C reduction

[0586] Except that the holding temperature of the pretreatment in Example 39 was set to 900°C, Ru / Ba 0.1 La 0.9 O x 900°C reduction.

[0587] (Example 43)

[0588] Ru / Ba 0.1 Ce 0.9 O x 500°C reduction

[0589] Except that in Example 39, Ce(NO3)3-6H2O was used instead of La(NO3)3-6H2O as the raw material and the holding temperature of the pretreatment was set to 500°C, Ru / Ba 0.1 Ce 0.9 O x 500°C reduction.

[0590] (Example 44)

[0591] Ru / Ba 0.1 Ce 0.9 O x 700°C reduction

[0592] Except that the holding temperature of the pretreatment in Example 43 was set to 700°C, Ru / Ba 0.1 Ce 0.9 Ox 700°C reduction.

[0593] The metal supports obtained in each of the examples were measured for ammonia synthesis activity and physical properties, etc. The results are shown in the following table.

[0594]

Table 5

[0595]

[0596] (Example 45)

[0597] < Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 20 wt%)

[0598] Except for using Co(NO3)2-6H2O instead of Ru in Example 20, Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 20 wt%).

[0599] (Example 46)

[0600] < Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 20 wt%)

[0601] Except for using acetylacetone Co(II): Co(CH3COCHCOCH3)2-2H2O (and Wako Pure Chemical Industries) instead of Co(NO3)2-6H2O in Example 45, Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 20 wt%).

[0602] (Example 47)

[0603] < Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 10 wt%)

[0604] Except for using half the amount of Co in Example 46, Co / Ba0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 10 wt%)

[0605] (Example 48)

[0606] <Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 30 wt%)

[0607] Except for using 1.5 times the amount of Co in Example 46, Co / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction (Co loading: 30 wt%)

[0608] (Example 49)

[0609] <Co / Ba 0.1 La 0.45 Ce 0.45 O x 500°C reduction (Co loading: 20 wt%)

[0610] Except for using acetylacetone Co(II): Co(CH3COCHCOCH3)2-2H2O (and Kanto Chemical Co., Inc.) instead of Co(NO3)2-6H2O in Example 45, Co / Ba 0.1 La 0.45 Ce 0.45 O x 500°C reduction (Co loading: 20 wt%)

[0611] (Example 50)

[0612] <Co / Ba 0.1 La 0.45 Ce 0.45 O x 650°C reduction (Co loading: 20 wt%)

[0613] Except for setting the holding temperature of the pretreatment in Example 46 to 650°C, Co / Ba 0.1 La 0.45 Ce 0.45 O x 650°C reduction (Co loading: 20 wt%)

[0614] (Example 51)

[0615] <Co / Ba 0.1 La 0.45 Ce 0.45 O x _ Reduction at 750°C (Co loading: 20 wt%)

[0616] Except that the holding temperature of the pretreatment in Example 46 was set to 750°C, Co / Ba 0.1 La 0.45 Ce 0.45 O x _ Reduction at 750°C (Co loading: 20 wt%)

[0617] (Example 52)

[0618] <Co / Ba 0.1 Ce 0.45 Pr 0.45 O x _ Reduction at 700°C (Co loading: 20 wt%)

[0619] Except that Co(NO3)2-6H2O was used instead of Ru in Example 10, and the holding temperature of the pretreatment was set to 700°C, Ru / Ba 0.1 Ce 0.45 Pr 0.45 O x _ Reduction at 700°C (Co loading: 20 wt%)

[0620] (Example 53)

[0621] <Ru / Ce 0.85 La 0.15 O x _ Reduction at 500°C

[0622] Except that the ratio of the raw material Ce to La in Example 1 was changed, Ru / Ce 0.85 La 0.15 O x _ Reduction at 500°C.

[0623] (Example 54)

[0624] <Ru / Ce 0.85 La 0.15 O x _ Reduction at 600°C

[0625] Except that the pretreatment holding temperature in Example 53 was set to 600°C, Ru / Ce was obtained through the same operation as in Example 54. 0.85 La 0.15 O x Reduced at 600℃.

[0626] (Example 55)

[0627] <Ru / Ce 0.85 La 0.15 O x _650℃ reduction>

[0628] Except that the pretreatment holding temperature in Example 53 was set to 650°C, Ru / Ce was obtained through the same operation as in Example 54. 0.85 La 0.15 O x Reduced at 650℃.

[0629] (Example 56)

[0630] <Ru / Ce 0.85 La 0.15 O x _700℃ reduction>

[0631] Except that the pretreatment holding temperature in Example 53 was set to 700°C, Ru / Ce was obtained through the same operation as in Example 54. 0.85 La 0.15 O x Reduced at 700℃.

[0632] (Example 57)

[0633] <Ru / Ce 0.67 La 0.33 O x _500℃ reduction>

[0634] Except for changing the ratio of raw materials Ce to La in Example 53, Ru / Ce was obtained by the same operation as in Example 53. 0.67 La 0.33 O x Reduced at 500℃.

[0635] (Example 58)

[0636] <Ru / Ce 0.67 La 0.33 O x _600℃ reduction>

[0637] Except that the pretreatment holding temperature in Example 57 was set to 600°C, Ru / Ce was obtained through the same operation as in Example 57.0.67 La 0.33 O x _600°C reduction.

[0638] (Example 59)

[0639] <Ru / Ce 0.67 La 0.33 O x _650°C reduction

[0640] Except that the holding temperature of the pretreatment in Example 57 was set to 650°C, Ru / Ce 0.67 La 0.33 O x _650°C reduction.

[0641] (Example 60)

[0642] <Ru / Ce 0.67 La 0.33 O x _700°C reduction

[0643] Except that the holding temperature of the pretreatment in Example 57 was set to 700°C, Ru / Ce 0.67 La 0.33 O x _700°C reduction.

[0644] (Example 61)

[0645] <Ru / Ce 0.33 La 0.67 O x _500°C reduction

[0646] Except that the ratio of the raw material Ce to La in Example 53 was changed, Ru / Ce 0.33 La 0.67 O x _500°C reduction.

[0647] (Example 62)

[0648] <Ru / Ce 0.33 La 0.67 O x _600°C reduction

[0649] Except that the holding temperature of the pretreatment in Example 61 was set to 600°C, Ru / Ce 0.33 La 0.67 O x _600°C reduction.

[0650] (Example 63)

[0651] Ru / Ce 0.33 La 0.67 O x 650°C reduction

[0652] Except that the holding temperature of the pretreatment in Example 61 was set to 650°C, Ru / Ce 0.33 La 0.67 O x 650°C reduction.

[0653] (Example 64)

[0654] Ru / Ce 0.33 La 0.67 O x 700°C reduction

[0655] Except that the holding temperature of the pretreatment in Example 61 was set to 700°C, Ru / Ce 0.33 La 0.67 O x 700°C reduction.

[0656] (Example 65)

[0657] Ru / Ce 0.15 La 0.85 O x 500°C reduction

[0658] Except that the ratio of the raw material Ce to La in Example 53 was changed, Ru / Ce 0.15 La 0.85 O x 500°C reduction.

[0659] (Example 66)

[0660] Ru / Ce 0.15 La 0.85 O x 600°C reduction

[0661] Except that the holding temperature of the pretreatment in Example 65 was set to 600°C, Ru / Ce 0.15 La 0.85 O x 600°C reduction.

[0662] (Example 67)

[0663] <Ru / Ce 0.15 La 0.85 O x 650°C reduction

[0664] Except that the holding temperature of the pre-treatment in Example 65 was set to 650°C, Ru / Ce 0.15 La 0.85 O x 650°C reduction.

[0665] (Example 68)

[0666] <Ru / Ce 0.5 La 0.5 O x 700°C reduction

[0667] Except that the holding temperature of the pre-treatment in Example 65 was set to 700°C, Ru / Ce 0.15 La 0.85 O x 700°C reduction.

[0668] (Example 69)

[0669] <Ru / Ce 0.5 La 0.5 O x 500°C reduction

[0670] Except that the ratio of the raw material Ce to La in Example 53 was changed, and the heating (firing) temperature was set to 600°C in the adjustment stage of the composite oxide, Ru / Ce 0.5 La 0.5 O x 500°C reduction.

[0671] (Example 70)

[0672] <Ru / Ce 0.5 La 0.5 O x 650°C reduction

[0673] Except that the holding temperature of the pre-treatment in Example 69 was set to 650°C, Ru / Ce 0.5 La 0.5 O x 650°C reduction.

[0674] (Example 71)

[0675] <Ru / Ce0.5 La 0.5 O x 800°C reduction

[0676] Example 69 except that the holding temperature of the pre-treatment in Example 69 was set to 800°C, by the same operation as Example 69, Ru / Ce 0.5 La 0.5 O x 800°C reduction.

[0677] The metal supports obtained in each of the examples and comparative examples were measured for ammonia synthesis activity and physical properties, etc. The results are shown in the following tables.

[0678] [Table 6]

[0679]

[0680] [Table 7]

[0681]

[0682] [Table 8]

[0683]

[0684] (Comparative Example 4)

[0685] Ru / La203_500°C reduction

[0686] La203was synthesized using a reverse heterogeneous precipitation method as follows. La(N03)3-6H20 (Wako Pure Chemical Industries) was dissolved in purified water (Takugawa Pharmaceutical) to form an aqueous La(N03)3solution. A support precursor solution containing a total of 0.0625 mol of La in 250 mL was prepared. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added to a 1000 mL beaker in 250 mL, while stirring with a magnetic stirrer at 320 rpm, the above support precursor solution was added all at once, and stirring was continued for 1 hour. After standing for 30 minutes, 350 mL of supernatant was removed, and after adding 350 mL of ion exchange water, stirring was performed for 30 minutes. The series of operations were performed four times, the precipitate was filtered, and the dried precipitate was pulverized with a mortar, and the obtained powder was heated at 700°C for 5 hours under an atmospheric atmosphere using an electric furnace, thereby obtaining La203. Ru was supported by the same operation as Example 1, and reduction treatment was performed by the same operation as Example 1, thereby obtaining Ru / La203_500°C reduction.

[0687] (Comparative Example 5)

[0688] Ru / CeO x_500°C reduction

[0689] CeO2composite oxide was synthesized using a reverse homogeneous precipitation method as follows. Ce(NO3)3-6H2O (Showa Chemical) was dissolved in purified water (Takugaku Pharmaceutical) to form an aqueous Ce(NO3)3solution. The aqueous Ce(NO3)3solution was mixed to prepare a 250 mL support precursor solution containing a total of 0.0625 mol of Ce. A 28% aqueous NH3solution (Wako Pure Chemical Industries) was added to 1000 mL of a beaker in 250 mL, while stirring with a magnetic stirrer at 320 rpm, the above support precursor solution was added all at once, and stirring was continued for 1 hour. After standing for 30 minutes, 350 mL of supernatant was removed, and after adding 350 mL of ion exchange water, stirring was performed for 30 minutes. The series of operations were performed four times, the precipitate was filtered, and the dried precipitate was pulverized with a mortar, and the obtained powder was heated at 700°C for 5 hours under an atmospheric atmosphere using an electric furnace, thereby obtaining CeO2. Ru was supported by the same operation as in Example 1, and reduction treatment was performed by the same operation as in Example 1, thereby obtaining Ru / CeO2_700°C reduction. x _500°C reduction.

[0690] (Comparative Example 6)

[0691] <Ru / CeO2_650°C reduction>

[0692] Except that the holding temperature of the pre-treatment in Comparative Example 5 was set to 650°C, Ru / CeO2_650°C reduction was obtained by the same operation as in Comparative Example 5.

[0693] (Example 75)

[0694] <Ru / La 0.5 Pr 0.5 O x _450°C reduction>

[0695] Except that the holding temperature of the pre-treatment in Example 5 was set to 450°C, Ru / La 0.5 Pr 0.5 O x _450°C reduction.

[0696] (Example 76)

[0697] <Ru / La 0.5 Pr 0.5 O 1.75 _500°C reduction>

[0698] Ru / La 0.5 Pr 0.5 O x reduction at 500°C.

[0699] (Example 78)

[0700] Ru / La 0.5 Pr 0.5 O x reduction at 700°C.

[0701] Ru / La 0.5 Pr 0.5 O x reduction at 700°C.

[0702] (Comparative Example 8)

[0703] Ru / MgO reduction at 700°C

[0704] Ru / MgO reduction at 700°C

[0705] (Example 80)

[0706] 8.4 wt% Ba / 4.5 wt% Ru / MgO reduction at 500°C

[0707] Preparation of Catalyst

[0708] After obtaining Ru / MgO using the method described in Comparative Example 8, Ba was supported by the evaporation drying method using Ba(OH)2-8H2O as a raw material for the Ru / MgO metal support in an amount 1.37 times as much as that of Ru.

[0709] Pre-treatment by hydrogen reduction

[0710] 8.4 wt% Ba / 4.5 wt% Ru / MgO reduction at 500°C

[0711] (Example 81)

[0712] 8.4 wt% Ba / 4.5 wt% Ru / MgO reduction at 700°C

[0713] Example 80 except that the holding temperature of the pretreatment in Example 80 was set to 700°C, 8.4wt% Ba / 4.5wt% Ru / MgO_700°C reduction was obtained by the same operation as in Example 80.

[0714] (Example 82)

[0715] <Ru / Ce 0.5 Pr 0.5 O x _500°C reduction

[0716] Example 1 except that, instead of the raw material La(N03)3-6H20, Pr(N03)3-6H20 was used, Ru / Ce 0.5 Pr 0.5 O x _500°C reduction.

[0717] (Example 83)

[0718] <Ru / Ce 0.5 Pr 0.5 O x _600°C reduction

[0719] Example 82 except that the holding temperature of the pretreatment in Example 82 was set to 600°C, Ru / Ce 0.5 Pr 0.5 O x _600°C reduction.

[0720] (Example 84)

[0721] <Ru / Ce 0.5 Pr 0.5 O x _650°C reduction

[0722] Example 82 except that the holding temperature of the pretreatment in Example 82 was set to 650°C, Ru / Ce 0.5 Pr 0.5 O2_650°C reduction.

[0723] (Example 85)

[0724] <Ru / Ce 0.5 Pr 0.5 O x _700°C reduction

[0725] Example 86) except that the holding temperature of the pre-treatment in Example 82 was set to 700°C, Ru / Ce 0.5 Pr 0.5 O x reduction at 700°C.

[0726] (Example 86)

[0727] Ru / Ce 0.5 Pr 0.5 O x reduction at 800°C.

[0728] Example 87) except that the holding temperature of the pre-treatment in Example 82 was set to 800°C, Ru / Ce 0.5 Pr 0.5 O x reduction at 800°C.

[0729] (Example 87)

[0730] Ru / Ce 0.5 La 0.5 O x reduction at 500°C.

[0731] Example 1 except that the heating (firing) temperature at the adjustment stage of the composite oxide was set to 800°C, and a gas purifier was used as in Example 20, Ru / Ce 0.5 La 0.5 O x reduction at 500°C.

[0732] (Example 88)

[0733] Ru / Ce 0.5 La 0.5 O x reduction at 650°C.

[0734] Example 87) except that the holding temperature of the pre-treatment in Example 87 was set to 650°C, Ru / Ce 0.5 La 0.5 O x reduction at 650°C.

[0735] (Example 89)

[0736] Ru / Ce 0.5 La 0.5 O x reduction at 800°C.

[0737] Example 87 except that the holding temperature of the pre-treatment was set to 800°C, Ru / Ce 0.5 La 0.5 O x 800°C reduction.

[0738] (Example 90)

[0739] <Fe / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0740] Example 20 except that tris(2,4-pentanedione)iron(III) (Fe(acac)3) was used instead of Ru as a raw material and the holding temperature of the pre-treatment was set to 700°C, Fe / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0741] (Example 91)

[0742] <Fe / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0743] Example 90 except that iron dodecacarbonyl (Fe3(CO) 12 ) was used instead of Fe(acac)3 as a raw material, Fe / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0744] (Example 92)

[0745] <Co-Fe / Ba 0.1 La 0.45 Ce 0.45 O x 700°C reduction.

[0746] Example 90 except that Co(NO3)2-6H2O was used as a raw material in addition to Fe(acac)3, Co-Fe / Ba 0.1 La 0.45 Ce 0.45 O x700°C reduction.

[0747] (Example 93)

[0748] <Co-Fe / Ba 0.1 La 0.45 Ce 0.45 O x 750°C reduction.

[0749] Except that the pre-treatment holding temperature in Example 92 was set to 750°C, Co-Fe / Ba 0.1 La 0.45 Ce 0.45 O x 750°C reduction.

[0750] (Example 94)

[0751] <Ru / Ba 0.1 La 0.3 Ce 0.6 O x 700°C reduction.

[0752] Except that the ratio of La to Ce in Example 23 was changed, Ru / Ba 0.1 La 0.3 Ce 0.6 O x 700°C reduction.

[0753] (Example 95)

[0754] <Ru / Ba 0.1 La 0.6 Ce 0.3 O x 700°C reduction.

[0755] Except that the ratio of La to Ce in Example 94 was changed, Ru / Ba 0.1 La 0.6 Ce 0.3 O x 700°C reduction.

[0756] (Example 96)

[0757] <Ru / Ba 0.1 La 0.8 Ce 0.1 O x 700°C reduction.

[0758] Ru / Ba 0.1 La 0.8 Ce 0.1 O x 700°C reduction.

[0759] (Example 97)

[0760] Ru / Ba 0.1 La 0.45 Ce 0.45 O x 500°C, 48 hours reduction.

[0761] Pre-treatment before hydrogen reduction

[0762] Ru / Ba 0.1 La 0.45 Ce 0.45 O x 500°C, 48 hours reduction.

[0763] (Example 98)

[0764] Ru / Ba 0.1 La 0.45 Ce 0.45 O x 450°C, 72 hours reduction.

[0765] Pre-treatment before hydrogen reduction

[0766] Ru / Ba 0.1 La 0.45 Ce 0.45 O x 450°C, 72 hours reduction.

[0767] (Example 99)

[0768] Ru / Ce 0.5 La 0.5 O x 500°C, 48 hours reduction.

[0769] Pre-treatment before hydrogen reduction

[0770] Ru / Ce 0.5 La0.5 O x 500°C for 48 hours reduction.

[0771] The metal supports obtained in each of the examples and comparative examples were measured for ammonia synthesis activity and physical properties, etc. The results are shown in the following tables.

[0772]

Table 9

[0773]

[0774]

Table 10

[0775]

[0776]

Table 11

[0777]

[0778] Confirmation of Solid Solution State of Support

[0779] Figure 6 are graphs showing the XRD patterns of Ru / Ba 0.1 La 0.45 Ce 0.45 O x (Example 6) and Ru / La 0.5 Ce 0.5 O x (Example 2). As shown in the graphs, the positions of the main diffraction peaks of Ba 0.1 La 0.45 Ce 0.45 O x did not change at all compared to the positions of the main diffraction peaks of La 0.5 Ce 0.5 O x When a part or all of Ba forms a solid solution with La, Ce, etc., the main diffraction peaks of Ba 0.1 La 0.45 Ce 0.45 O x should move to the low angle side because Ba with a large ionic radius exists within the crystal lattice. Therefore, this means that Ba did not form a solid solution with La, Ce, etc.

[0780] Figure 7 are graphs showing the results of the analysis of the catalyst of Example 6 (Ru / Ba 0.1 La 0.45 Ce 0.45 O xThe results of the analysis of the surface of the catalyst (1) are shown in FIG. 6. In this figure, the composition of Ba, La, and Ce on the surface of the catalyst is analyzed, and the brightness and darkness are used to indicate the concentration. That is, the higher the concentration of each element, the brighter it is shown in the figure. From the figure, it is known that La and Ce are present almost uniformly in the catalyst particles, and are not present in high concentration in any particular area.

[0781] On the other hand, it is known that Ba is present in a concentration gradient, and is distributed in a particularly high concentration in the central area of the field of view. From the above results, it is known that Ba is not present in a solid solution with La and Ce.

Claims

1. A method for manufacturing a metal support using a composite oxide, characterized in that, The composite oxide contains metallic elements represented by the general formula (1): A n X y M m (1), In the general formula (1), A is a lanthanide element characterized by at least some or all of it being in the III valence state. X is any element selected from Group 2 of the periodic table and the lanthanides, chosen from the group consisting of Ca, Sr, and Ba, and represents an element different from A. M is any one of the elements selected from Group 1 elements of the periodic table, Group 2 elements selected from the group consisting of Ca, Sr, and Ba, and the lanthanides, and represents an element different from A and X. n satisfies 0 < n < 1, y satisfies 0 < y < 1, m satisfies 0 ≤ m < 1. And n + y + m = 1, The manufacturing method includes: The mixing step involves mixing an A precursor containing A, an X precursor containing X, and an M precursor containing M to obtain a mixture; and The firing step involves firing the mixture at a temperature above 600°C to obtain a carrier composed of composite oxides. The loading step involves loading a compound containing a transition metal other than Group 4 onto the composite oxide to formulate a support prior to reduction treatment; and The reduction step involves subjecting the loading to reduction treatment at a temperature above 400°C in a hydrogen-containing atmosphere. Furthermore, the firing temperature is higher than the reduction temperature.

2. The method for manufacturing a metal support as described in claim 1, wherein, Number of moles of the III valence state (A) 3＋ ) and the total number of moles of A (A total The ratio of (A) to 3＋ / A total ) satisfies 0.1≤A 3＋ / A total ≤1.

0.

3. The method for manufacturing a metal support as described in claim 1, wherein, The composite oxide comprises a solid solution of tetragonal or cubic crystals.

4. The method for manufacturing a metal support as described in claim 1, wherein, The composite oxide contains at least one of the elements A, X, and M, which is a partially negatively charged (-δ) oxygen in the oxide state. O A strong alkaline element with a value of 0.50 or higher.

5. The method for manufacturing a metal support as described in claim 1, wherein, When the composition ratio of each element in the composite oxide is represented by ni, and the Sanderson electronegativity of each element is represented by χi, the value of the partial negative charge of oxygen (-δ) shown in the following equation (A) is... O () is above 0.52: ((For example ni ) 1 / Σni ―5.21) / -4.75・・(A), Where i represents all elements in the composite oxide including A, X, M, and O.

6. The method for manufacturing a metal support as described in claim 1, characterized in that, The composite oxide is a binary composite oxide represented by the general formula (1) as shown in the following general formula (1-1). A n X y (1-1), Furthermore, the composite oxide is a solid solution of A and X. Wherein, A, X, n, and y are as defined in claim 1.

7. The method for manufacturing a metal support as described in claim 1, characterized in that, The composite oxide is a ternary composite oxide represented by the general formula (1) as shown in the following general formula (1-2). A n X y M m (1-2), Furthermore, the composite oxide is in a solid solution state of an oxide formed from one of A and X or M, and a mixture state of an oxide from the other of X or M. Wherein, A, X, M, n, y, and m are as defined in claim 1.

8. The method for manufacturing a metal support as described in claim 1, characterized in that, In the general formula (1), X is Ba, and the amount of carbonate ions contained in the composite oxide is less than 10 mol% compared with Ba.

9. The method for manufacturing a metal support as described in claim 1, characterized in that, In the firing step, the mixture is fired at a temperature below 800°C.

10. A method for manufacturing a metal support using a composite oxide, characterized in that, The composite oxide is represented by the following general formula (2): A n X 1-n M m O x (2), In the general formula (2), A is a rare earth element characterized by at least a portion of it being in a state of trivalent oxidation state. X is any one of Group 2, Group 4, and rare earth elements in the periodic table, and represents an element different from A. M is any one of Group 2, Group 4, and rare earth elements in the periodic table, and represents an element different from A and X. n satisfies 0 < n < 1, m satisfies 0 ≤ m < 0.

5. x represents the number of oxygen atoms required for the composite oxide to maintain its electroneutrality. The manufacturing method includes: The mixing step involves mixing an A precursor containing A, an X precursor containing X, and an M precursor containing M to obtain a mixture; and The firing step involves firing the mixture at a temperature above 600°C to obtain a carrier composed of composite oxides. The loading step involves loading a compound containing a transition metal other than Group 4 onto the composite oxide to formulate a support prior to reduction treatment; and The reduction step involves subjecting the loading to reduction treatment at a temperature above 400°C in a hydrogen-containing atmosphere. Furthermore, the firing temperature is higher than the reduction temperature.

11. The method for manufacturing a metal support as described in claim 10, characterized in that, The transition metal is Ru, and the Ru dispersion value (D) was determined by H2 pulse chemisorption. ads ), and the value of Ru dispersion predicted based on the average particle diameter of Ru particles obtained from TEM images (D TEM The ratio of ) satisfies: 0<D ads / D TEM <1。 12. The method for manufacturing a metal support as described in claim 10, characterized in that, When nitrogen is adsorbed onto the supported transition metal, infrared absorption spectroscopy revealed that the N≡N stretching vibration ν1 of the nitrogen molecules interacting along the long axis ranged from 2300 to 2000 cm⁻¹. -1 And / or, weakened N≡N stretching vibrations ν² of nitrogen molecules interacting with the transition metal along the long axis were observed to be 1900–1500 cm⁻¹. -1 .

13. The method for manufacturing a metal support as described in claim 10, characterized in that, The average particle diameter of the transition metal supported on the composite oxide is less than 100 nm.

14. The method for manufacturing a metal support as described in claim 10, characterized in that, In the firing step, the mixture is fired at a temperature below 800°C. In the reduction step, the support before reduction treatment is calcined at a temperature above 500°C and in a hydrogen-containing atmosphere for more than 2 hours.

15. A method for manufacturing a catalyst for ammonia synthesis, characterized in that, The step includes manufacturing a catalyst for ammonia synthesis using a metal support manufactured by the method for manufacturing a metal support as described in claim 10.

16. A method for producing ammonia, comprising contacting hydrogen and nitrogen with a catalyst to produce ammonia, characterized in that, The catalyst is an ammonia synthesis catalyst manufactured by the method for manufacturing an ammonia synthesis catalyst as described in claim 15.

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