Metal-supported material and ammonia synthesis catalyst
A metal-supported material including a transition metal excluding Group 4 elements supported on a binary composite oxide. The composite oxide includes a metal element expressed by A n X y , where A represents a lanthanoid that is in a partially or entirely trivalent state, X represents an element that is a Group-2 element in a periodic table selected from the group consisting of Ca, Sr, and Ba, or a lanthanoid, and that is different from A, n satisfies 0<n<1, y satisfies 0<y<1, m satisfies 0≤m<1, and n+y=1. The composite oxide includes a solid solution that is a tetragonal crystal or a cubic crystal, and a ratio of a value (D ads ) of a dispersion degree of the transition metal obtained by an H 2 pulse chemical adsorption method to a value (D TEM ) of the dispersion degree predicted from an average particle diameter of particles of the transition metal obtained from a TEM image satisfies 0<D ads /D TEM <1.
1 . A metal-supported material in which ruthenium particles are supported on a composite oxide expressed by General Formula (2):
A n X 1−n O x (2)
where A represents an element selected from the group consisting of Ce, Pr, and Tb, that is in a trivalent state at least partially, and a ratio of moles of the element in the trivalent state to total moles of the element in both a tetravalent state and the trivalent state is 0.1 to 0.9,
X represents an element selected from the group consisting of Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and that is different from A,
n satisfies 0<n<1, and
x represents the number of oxygen atoms necessary for the composite oxide to keep neutral electrically;
wherein the composite oxide includes a solid solution that is a tetragonal crystal or a cubic crystal,
wherein a ratio of a value (D ads ) of a ruthenium dispersion degree obtained by an H 2 pulse chemical adsorption method to a value (D TEM ) of a ruthenium dispersion degree expected from an average particle diameter of ruthenium particles obtained from a TEM image satisfies 0<D ads /D TEM <1, and
wherein the metal-supported material is manufactured by:
mixing an A precursor including A and an X precursor including X to obtain a mixture;
calcinating the mixture at 600° C. or more to obtain a carrier including the composite oxide;
supporting a compound including ruthenium on the composite oxide to prepare a before-reducing process supporting material; and
performing a reducing process on the before-reducing process supporting material at 400° C. or more.
2 . The metal-supported material according to claim 1 , wherein at least one of the elements A and X in the composite oxide is an element with strong basicity for which a value of a partial negative charge (−δ o ) of oxygen in an oxide state is 0.50 or more.
3 . The metal-supported material according to claim 1 , wherein when a composition ratio of each element in the composite oxide is ni, where i represents all the elements in the composite oxide including A, X, and O, and a Sanderson electronegativity of each element is χi, where i represents all the elements in the composite oxide including A, X, and O, a value of a partial negative charge (−δ o ) of oxygen expressed by the following Formula is 0.52 or more:
((Π(χi ni )){circumflex over ( )}(1/ Σni )−5.21)/−4.75.
4 . The metal-supported material according to claim 1 , wherein X is Ba and a quantity of carbonate ions included in the composite oxide is 10 mol % or less of Ba.
5 . The metal-supported material according to claim 1 , wherein when nitrogen is adsorbed on the supported ruthenium particles, N≡N stretching vibration υ1 of nitrogen molecules that mutually act in a major-axis direction is observed in 2300 to 2000 cm −1 by an infrared absorption spectroscopy.
6 . The metal-supported material according to claim 1 , wherein when nitrogen is adsorbed on the supported ruthenium particles, weakened N≡N stretching vibration υ2 of the nitrogen molecules that mutually act in the major-axis direction for the transition metal is observed in 1900 to 1500 cm −1 by an infrared absorption spectroscopy.
7 . The metal-supported material according to claim 1 , wherein an average particle diameter of the ruthenium particles supported on the composite oxide is 100 nm or less.
8 . An ammonia synthesis catalyst comprising the metal-supported material according to claim 1 .
9 . A manufacturing method for ammonia comprising bringing hydrogen, nitrogen, and a catalyst in contact with each other, wherein the catalyst is the ammonia synthesis catalyst according to claim 8 .