Ammonia synthesis catalyst

1 . A metal-carrier material comprising a composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, the composite oxide represented by a composition of general formula (1):

L n N 1-n   (1)

the composite oxide having the following characteristics (a) to (d):

(a) the metal element L being an oxide of any element(s) selected from the group consisting of Ba and Sr,

(b) the metal element N comprising a Group 1 or Group 2 element other than the metal element L,

(c) n of 0.001 or more and 0.300 or less, and

(d) the oxide of the metal element L and the oxide of the metal element N forming no solid solution, and oxide particles of the metal element L being deposited on surfaces of oxide particles of the metal element N,

the composite oxide having, supported thereon, particles of at least one metal M selected from the group consisting of Ru, Fe, Co, Ni, Rh, Pd, Os, Ir, and Pt,

wherein the metal particles M are supported on the oxide of the metal element L and oxide of the metal element L are deposited on surfaces of the metal particles M,

and wherein the metal particles M are not in direct contact with the oxide of the metal element N.

2 . A metal-carrier material comprising a composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, the composite oxide represented by a composition of general formula (1):

L n N 1-n   (1)

the composite oxide having the following characteristics (a) to (d):

(a) the metal element L being an oxide of any element(s) selected from the group consisting of:

(i) a Group 1 element,

(ii) a Group 2 element, or

(iii) a Group 1 element and a Group 2 element,

(b) the metal element N comprising a Group 1 or Group 2 element other than the metal element L,

(c) n of 0.001 or more and 0.300 or less, and

(d) the oxide of the metal element L and the oxide of the metal element N forming no solid solution, and oxide particles of the metal element L being deposited on surfaces of oxide particles of the metal element N,

wherein the composite oxide has, supported thereon, particles of cobalt.

3 . An ammonia synthesis catalyst comprising the metal-carrier material according to claim 1 .

4 . A method of producing the metal-carrier material according to claim 1 , comprising the steps of (a) to (d):

(a) impregnating a metal element N-containing N precursor with a metal element L-containing L precursor;

(b) calcinating the resulting mixture at a temperature of 500° C. or higher to obtain a carrier including a composite oxide;

(c) impregnating the composite oxide with metal particles M-containing compound precursor to obtain an impregnated carrier; and

(d) calcinating the impregnated carrier at a temperature of 400° C. or higher.

5 . The method of producing a metal-carrier material according to claim 4 , further comprising step (e):

(e) calcinating the resulting metal-carrier material obtained in (d) at 500° C. or higher in a presence of hydrogen.

6 . A method of producing ammonia, comprising bringing hydrogen and nitrogen into contact with a catalyst, the catalyst being the ammonia synthesis catalyst according to claim 3 .

7 . The metal carrier material according to claim 1 , wherein the metal element N represents a metal element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less.

8 . The metal carrier material according to claim 1 , wherein the composite oxide is a binary composite oxide consisting of a metal element A contained in the metal element L and a metal element B contained in the metal element N, wherein the general formula (1) is represented by a composition of general formula (2):

A n B 1-n   (2)

the composite oxide having the following characteristics (a) to (c);

(a) the metal element B representing a Group 2 element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less,

(b) n of 0.001 or more and 0.300 or less, and

(c) an oxide of the metal element A and an oxide of the metal element B forming no solid solution, and oxide of the metal element A being deposited on surfaces of oxide particles of the metal element B.

9 . The metal carrier material according to claim 1 , wherein the general formula (1) is represented by a composition of general formula (3):

L n N 1-n O x   (3)

the composite oxide having the following characteristics (a) to (e):

(a) the metal element L being an oxide of any element(s) selected from the group consisting of Ba and Sr,

(b) the metal element N comprising a Group 1 or Group 2 element other than the metal element L,

(c) n of 0.001 or more and 0.300 or less,

(d) the oxide of the metal element L and the oxide of the metal element N forming no solid solution, and oxide of the metal element L being deposited on surfaces of oxide particles of the metal element N, and

(e) x is the number of oxygen atoms required to keep the composite oxide electrically neutral.

10 . The metal carrier material according to claim 9 , wherein the metal element N represents a metal element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less.

11 . The metal carrier material according to claim 9 , wherein the composite oxide is a binary composite oxide consisting of a metal element A contained in the metal element L and a metal element B contained in the metal element N, wherein the general formula (3) is represented by a composition of general formula (4):

A n B 1-n O x   (4)

the composite oxide having the following characteristics (a) to (d);

(a) the metal element B representing a Group 2 element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less,

(b) n of 0.001 or more and 0.300 or less,

(c) an oxide of the metal element A and an oxide of the metal element B forming no solid solution, and oxide of the metal element A being deposited on surfaces of oxide particles of the metal element B, and

(d) x is the number of oxygen atoms required to keep the composite oxide electrically neutral.

12 . The metal carrier material according to claim 1 , wherein the composite oxide is Ba n Mg 1-n O x , where 0.001≤n≤0.300.

13 . The metal carrier material according to 12, wherein an amount of carbonate contained in the composite oxide is 10 mol % or less based on Ba.

14 . The metal carrier material according to claim 2 , wherein the metal element N represents a metal element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less.

15 . The metal carrier material according to claim 2 , wherein the composite oxide is a binary composite oxide consisting of a metal element A contained in the metal element L and a metal element B contained in the metal element N, wherein the general formula (1) is represented by a composition of general formula (2):

A n B 1-n   (2)

the composite oxide having the following characteristics (a) to (c);

(a) the metal element B representing a Group 2 element that is a weakly basic element having a value of partial negative charge (−δ OB ) of oxygen in an oxide state of 0.35 or more and 0.55 or less,

(b) n of 0.001 or more and 0.300 or less, and

(c) an oxide of the metal element A and an oxide of the metal element B forming no solid solution, and oxide particles of the metal element A being deposited on surfaces of oxide particles of the metal element B.

16 . The metal carrier material according to claim 2 , wherein the general formula (1) is represented by a composition of general formula (3):

L n N 1-n O x   (3)

the composite oxide having the following characteristics (a) to (e):

(a) the metal element L being an oxide of any element(s) selected from the group consisting of Ba and Sr,

(b) the metal element N comprising a Group 1 or Group 2 element other than the metal element L,

(c) n of 0.001 or more and 0.300 or less,

(d) the oxide of the metal element L and the oxide of the metal element N forming no solid solution, and oxide of the metal element L being deposited on surfaces of oxide particles of the metal element N, and

(e) x is the number of oxygen atoms required to keep the composite oxide electrically neutral.

17 . The metal carrier material according to claim 16 , wherein the composite oxide is a binary composite oxide consisting of a metal element A contained in the metal element L and a metal element B contained in the metal element N, wherein the general formula (3) is represented by a composition of general formula (4):

A n B 1-n O x   (4)

the composite oxide having the following characteristics (a) to (d);

(a) the metal element B representing a Group 2 element that is a weakly basic element having a value of partial negative charge of oxygen in an oxide state of 0.35 or more and 0.55 or less,

(b) n of 0.001 or more and 0.300 or less,

(c) an oxide of the metal element A and an oxide of the metal element B forming no solid solution, and oxide of the metal element A being deposited on surfaces of oxide particles of the metal element B, and

(d) x is the number of oxygen atoms required to keep the composite oxide electrically neutral.

18 . The metal carrier material according to claim 2 , wherein the composite oxide is Ba n Mg 1-n O x , where 0.001≤n≤0.300.

19 . An ammonia synthesis catalyst comprising the metal-carrier material according to claim 2 .

20 . A method of producing ammonia, comprising bringing hydrogen and nitrogen into contact with a catalyst, the catalyst being the ammonia synthesis catalyst according to claim 19 .