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Supported metal catalyst and method of synthesizing ammonia using the same

Foreign code F170009049
File No. J1014-10WO
Posted date Apr 26, 2017
Country United States of America
Application number 201515121702
Gazette No. 20160361712
Date of filing Feb 12, 2015
Gazette Date Dec 15, 2016
International application number JP2015053853
International publication number WO2015129471
Date of international filing Feb 12, 2015
Date of international publication Sep 3, 2015
Priority data
  • P2014-037370 (Feb 27, 2014) JP
  • 2015JP53853 (Feb 12, 2015) WO
Title Supported metal catalyst and method of synthesizing ammonia using the same
Abstract A catalyst is provided which is used for continuously synthesizing ammonia using a gas containing hydrogen and nitrogen as a raw material, wherein a transition metal which exhibits catalytic activity is supported by a support, and the support is a two-dimensional electride or a precursor thereof.The two-dimensional electride or the precursor thereof is a metal nitride represented by MxNyHz (M represents one or two or more of Group II metals selected from the group consisting of Mg, Ca, Sr and Ba, and x, y and z are in ranges of 1≤x≤11, 1≤y≤8, and 0≤z≤4 respectively, in which x is an integer, and y and z are not limited to an integer) or M3N2 (M is the same as above), or a metal carbide selected from the group consisting of Y2C, Sc2C, Gd2C, Tb2C, Dy2C, Ho2C and Er2C.These catalysts are used for continuously reacting nitrogen with hydrogen, which are raw materials, on the catalyst, wherein the reaction is performed in an ammonia synthesis reaction system under the preferable conditions of a reaction temperature which is equal to or higher than 100° C. and equal to or lower than 600° C., and a reaction pressure which is equal to or higher than 10 kPa and lower than 20 MPa.
Outline of related art and contending technology BACKGROUND ART
Alkaline earth metal nitride represented by M3N2 (M represents Ca, Sr or Ba) is used for a raw material of aluminum nitride which is used in a semiconductor device, ceramic particles for a metal sliding member, a material for forming a battery electrode, conductive fine particles, and the like (Patent Document 1).Patent Document 1 discloses a method of producing M3N2 (M represents Be, Mg, Ca, Sr or Ba), M2N (M represents Be, Mg, Ca, Sr or Ba) or the like, wherein a Group II metal amide is thermally decomposed, and Patent Document 2 discloses a method of producing high-purity M3N2 (M represents Be, Mg, Ca, Sr or Ba), wherein ammonia is reacted with a Group II metal to be liquefied, and the obtained Group II metal amide is thermally decomposed.
As a calcium nitride, α-Ca3N2, β-Ca3N2, γ-Ca3N2, Ca11N8, Ca2N and the like are known.In addition, Ca2NH, CaNH, Ca (NH2)2 and the like (hereinafter, may be referred as a “Ca―N―H-based compound” in some cases), which are hydrides of the calcium nitride are also known.
Ca3N2 is obtained by dissolving Ca in liquid ammonia and performing thermal decomposition under a nitrogen atmosphere.As shown in the following formula, Ca3N2 reacts with moisture in air to generate calcium hydroxide and ammonia.This reaction also occurs in water.
Ca3N2+6H2O→3Ca(OH)2+2NH3
In addition, it is known that Ca2N is easily oxidized, and is a very unstable material.It has been informed that Ca2N can stably exist in Ar in a range which is equal to or less than 1000° C., or in nitrogen in a range which is between 250° C. to 800° C. (Non Patent Document 1).
On the other hand, in 2013, the present inventors found that Ca2N is a two-dimensional electride (Non Patent Document 2).Ca2N:e- is a layered compound in which electrons are linked with each other as an anion between layers formed by [Ca2N]+, and is obtained by heating Ca3N2 and metal Ca in a vacuum.It has been reported that a conductive electron concentration of Ca2N:e- is 1.39×1022/cm3, and a work function thereof is 2.6 eV.Thereafter, the two-dimensional electride is reported in Non Patent Document 3.
Further, the application for a patent has been filed by the present inventors with respect to an invention relating to a nitride electride which consists of a nitride, wherein the nitride has a layered crystal structure and is represented by ion formula [AE2N]+e- (AE represents at least one element selected from Ca, Sr and Ba) (Patent Document 3).
On the other hand, as a synthesis of ammonia in which a gas containing hydrogen and nitrogen is used as a raw material, a Haber-Bosch method which uses an iron oxide as a catalyst and uses alumina or potassium oxide as a promoter has been widely used, and the synthesis method has not been significantly changed for the past 100 years.The synthesis of ammonia according to the Haber-Bosch method is performed by reacting nitrogen and hydrogen gases on the catalyst under a high temperature and a high pressure, which are in a range of 300° C. to 500° C. and in a range of 20 to 40 MPa.
As a catalyst used for synthesizing ammonia, a ternary nitride of a Group VIII metal and a Group VIB metal (Patent Document 4), a cobalt-molybdenum composite nitride (Patent Document 5) and the like are known.The present inventors have developed a supported metal catalyst in which a mayenite type compound is used as a support of an ammonia synthesis catalyst (Patent Documents 6 and 7, and Non Patent Documents 4 and 5).
Scope of claims [claim1]

1-9. (canceled)
[claim2]
10. A supported metal catalyst, comprising:
a transition metal which exhibits catalytic activity,
wherein the transition metal is supported by a support, and
the support is a two-dimensional electride or a precursor thereof.
[claim3]
11. The supported metal catalyst according to claim 10, wherein the supported metal catalyst is a catalyst suitable for synthesizing ammonia.
[claim4]
12. The supported metal catalyst according to claim 10, wherein the supported metal catalyst is a catalyst suitable for synthesizing ammonia, wherein a gas comprising hydrogen and nitrogen is used as a raw material.
[claim5]
13. The supported metal catalyst according to claim 11, wherein the ammonia is synthesized continuously.
[claim6]
14. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is a metal nitride represented by MxNyHz or a hydride thereof,
wherein
M represents one or two or more of Group II metals selected from the group consisting of Mg, Ca, Sr and Ba, and
x, y and z are in ranges of 1≦x≦11, 1≦y≦8, and 0≦z≦4 respectively, in which x is an integer, and y and z are not limited to an integer.
[claim7]
15. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is a metal nitride represented by M3N2, wherein M represents one or two or more of Group II metals selected from the group consisting of Mg, Ca, Sr and Ba.
[claim8]
16. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is at least one selected from the group consisting of Ca2N, Sr2N, Ba2N, Ca2NH, CaNH, Ca(NH2)2, Y2C, Sc2C, Gd2C, Tb2C, Dy2C, Ho2C and Er2C.
[claim9]
17. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof comprise at least one compound selected from the group consisting of Ca2N, Sr2N and Ba2N, wherein a part of Ca of Ca2N, Sr of Sr2N, and Ba of Ba2N is substituted with at least one or more of alkaline metal elements selected from the group consisting of Li, Na, K, Rb and Cs.
[claim10]
18. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is at least one of Ca3N2 and Mg3N2.
[claim11]
19. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is a metal carbide selected from the group consisting of Y2C, Sc2C, Gd2C, Tb2C, Dy2C, Ho2C and Er2C, or is a hydride thereof.
[claim12]
20. The supported metal catalyst according to claim 10, wherein the two-dimensional electride or a precursor thereof is a Ca―N―H-based compound.
[claim13]
21. The supported metal catalyst according to claim 10, wherein the transition metal is at least one selected from the group consisting of Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh and Ir.
[claim14]
22. The supported metal catalyst according to claim 10, wherein the transition metal is at least one selected from the group consisting of Ru, Co and Fe.
[claim15]
23. The supported metal catalyst according to claim 10, wherein an amount of the transition metal is in a range of 0.01 to 30 wt % with respect to that of the support.
[claim16]
24. A method of synthesizing ammonia, comprising:
preparing
(a) a supported metal catalyst, wherein a transition metal which exhibits catalytic activity is supported by a support and the support is a two-dimensional electride or a precursor thereof, and
(b) gas comprising hydrogen and the nitrogen, which is used as a raw material; and
reacting the nitrogen with the hydrogen on the catalyst in an ammonia synthesis reaction device, in which the supported metal catalyst is provided, to synthesize ammonia.
[claim17]
25. The method of synthesizing ammonia according to claim 24, wherein the reaction of the nitrogen and the hydrogen is performed at a reaction temperature which is equal to or higher than 100° C. and equal to or lower than 600° C.
[claim18]
26. The method of synthesizing ammonia according to claim 24, wherein the reaction of the nitrogen and the hydrogen is performed at a reaction pressure which is equal to or higher than 10 kPa and lower than 20 MPa.
  • Inventor, and Inventor/Applicant
  • HOSONO Hideo
  • HARA Michikazu
  • KITANO Masaaki
  • YOKOYAMA Toshiharu
  • INOUE Yasunori
  • KAMBARA Shinji
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • TOKYO INSTITUTE OF TECHNOLOGY
IPC(International Patent Classification)
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