Top > Search of International Patents > Composite body, method for producing composite body, ammonia synthesis catalyst, and ammonia synthesis method

Composite body, method for producing composite body, ammonia synthesis catalyst, and ammonia synthesis method UPDATE_EN

Foreign code F180009409
File No. J1014-19WO
Posted date Apr 20, 2018
Country EPO
Application number 15864436
Gazette No. 3228386
Gazette No. 3228386
Date of filing Dec 4, 2015
Gazette Date Oct 11, 2017
Gazette Date Apr 22, 2020
International application number JP2015084207
International publication number WO2016088896
Date of international filing Dec 4, 2015
Date of international publication Jun 9, 2016
Priority data
  • P2014-246717 (Dec 5, 2014) JP
  • 2015JP84207 (Dec 4, 2015) WO
Title Composite body, method for producing composite body, ammonia synthesis catalyst, and ammonia synthesis method UPDATE_EN
Abstract An ammonia synthesis catalyst having high activity is obtained by having a two-dimensional electride compound having a lamellar crystal structure such as Ca 2 N support a transition metal. However, since the two-dimensional electride compound is unstable, the stability of the catalyst is low. In addition, in cases where a two-dimensional electride compound is used as a catalyst support, it is difficult to shape the catalyst depending on reactions since the two-dimensional electride compound has poor processability. A composite which includes a transition metal, a support and a metal amide compound, wherein the support is a metal oxide or a carbonaceous support; and the metal amide compound is a metal amide compound represented by general formula (1). M(NH 2 ) x ···(1) (In general formula (1), M represents at least one metal atom selected from the group consisting of Li, Na, K, Be, Mg, Ca, Sr, Ba and Eu; and x represents the valence of M.)
Outline of related art and contending technology Background Art
Alkaline earth metal nitrides such as Ca3N2, Sr3N2, Ba3N2 or the like are compounds which are used as raw materials of aluminum nitride for semiconductor devices, ceramic particles for metal sliding members, battery electrode constituent materials, conductive fine particles, or the like. Patent Document 1 discloses a method of producing an alkaline earth metal nitride by thermally decomposing a corresponding alkaline earth metal amide. In addition, Patent Document 2 discloses a method of producing a high purity metal nitride by reacting ammonia with an alkaline earth metal to make it liquid-phase, and then thermally decomposing the obtained metal amide compound.
Patent Document 3 discloses a method for producing a metal amide compound by reacting a metal hydride or a metal hydride in which a simple substance metal or an alloy is further added with liquid ammonia. As another method of producing metal amide such as LiNH2, Ca(NH2)2 or the like by enclosing a metal such as Li or Ca or a compound thereof in a reaction vessel, and after cooling, introducing ammonia having a volume ratio of 10 times or more with respect to metal and liquefying the ammonia, and then reacting them while stirring (Patent Document 4).
Calcium nitride which is a typical alkaline earth metal nitride is known as α-Ca3N2, β-Ca3N2, γ-Ca3N2, Ca11N8, Ca2N, or the like. Ca2NH, CaNH, Ca(NH2)2 or the like which are hydrides of calcium nitrides (hereinafter also referred to as "Ca-N-H based compounds") are also known.
It is known that Ca2N is a very chemically unstable substance. For example, it is readily oxidized. It has been reported that Ca2N can stably exist at 1000°C or less in Ar, or between 250°C and 800°C in nitrogen (Non-Patent Document 1).
On the other hand, the present inventors have found that a nitride represented by AE2N (AE represents at least one element selected from Ca, Sr, and Ba) is a "two-dimensional electride compound" having high conductivity (see Patent Document 5). The two-dimensional electride compound AE2N is a layered compound in which electron (e-) is bound as an anion between layers composed of [AE2N]+. That is, it can also be expressed as AE2N+:e- in the ionic formula.
For example, Ca2N, which is a typical two-dimensional electride compound, is obtained by heating Ca3N2 and metal Ca in vacuum. It has been reported that the conduction electron concentration of Ca2N is 1.4×1022/cm3 and has a work function of 2.6 eV (Non-Patent Document 2). Thereafter, an example in which this two-dimensional electride is used as a reducing agent for pinacol coupling has been reported (Non-Patent Document 3).
It has been reported that Ca(NH2)2 acts as a base catalyst and exhibits catalytic activity against an isomerization reaction of olefins such as 2-methyl-1-butene (Non-Patent Document 4). Another example is a catalyst in which an amide compound of Na, K, Eu, Yb is supported on an oxide support such as Al2O3. It exhibits catalytic activity for an olefin isomerization reaction such as 2-methyl-1-butene has been reported (Non-Patent Document 5). It has been reported that each example functions as a base catalyst.
For ammonia synthesis, a method using a catalyst containing Fe3O4 and several mass% of Al2O3 and K2O in Fe3O4 (Haber-Bosch method) is generally used. In addition, iron-based catalysts and Ru-based catalysts (for example, Ru/MgO, Ru/CaO, Ru-Cs/MgO) have been studied as synthesis methods other than the Harbor-Bosch method (Non-Patent Documents 6 and 7). These catalysts are catalysts in which a transition metal having ammonia synthesizing activity is supported on a support, and are generally referred to as "supported metal catalysts".
Other supported metal catalysts for ammonia synthesis include transition metals of Group 8 or 9 of the Periodic Table such as Fe, Ru, Os, Co, nitrides of transition metals of Group 8 or 6B of the periodic table, composite nitrides of Co · Mo and the like are used (Patent Documents 6 to 9). Also, an ammonia synthesis catalyst is known in which Al2O3, SiO2, Mg2O or magnesium aluminum spinel is used as a sub-support and Ru is supported on silicon nitride or boron nitride supported thereon (Patent Document 10).
Then, the present inventors have found that a transition metal supported on the two-dimensional electride becomes an ammonia synthesis catalyst having high activity. Specifically, a supported metal catalyst in which a transition metal such as Ru or Fe was supported on a metal nitride represented by MxNyHz (M is Mg, Ca, Sr, And Ba, x is an integer satisfying 1≦x≦11, y satisfies 1≦y≦8 and z satisfies 0≦z≦4.) or its hydride is a catalyst for ammonia synthesis (Patent Document 11). However, there is no report regarding a composite in which a metal amide compound and a metal are supported on a support, and a supported metal catalyst of the same.
Patent literature
Patent Document 1: Japanese Unexamined Patent Publication No. 2011-178648
Patent Document 2: Japanese Unexamined Patent Publication No. 2012-66991
Patent Document 3: Japanese Unexamined Patent Publication No. 2006-8440
Patent Document 4: Japanese Unexamined Patent Publication No. 2010-222213
Patent Document 5: Japanese Unexamined Patent Publication No. 2014-24712
Patent Document 6: Japanese Examined Patent Publication No. 51-47674
Patent Document 7: Japanese Examined Patent Publication No. 54-37592
Patent Document 8: Japanese Examined Patent Publication No. 59-16816
Patent Document 9: Japanese Unexamined Patent Publication No. 2000-264625
Patent Document 10: Japanese Unexamined Patent Publication No. 2004-35399
Patent Document 11: WO2015 / 129471

Non-Patent literature
Non-Patent Document 1: P. Hchn, S. Hoffmann, J. Hunger, S. Leoni, F. Nitsche, W. Schnelle, R. Kniep, Chem. Eur. J., 15, 3419 (2009)
Non-Patent Document 2: K. Lee, S. W. Kim, Y. Toda, S. Matsuishi and H. Hosono "Nature", 494, 336-341 (2013)
Non-Patent Document 3: Y. J. Kim, S. M. Kim, H. Hosono, J. W. Yang and S. W. Kim, Chemical Communications, 50, 4791-4794 (2014)
Non-Patent Document 4: I. V. Gostunskaya, N. I. Tyun'kina and B. A. Kazanskii, Doklady Akademii Nauk SSSR, 108, 473-6 (1956)
Non-Patent Document 5: Y. Ono and T. Baba, Catalysis Today, 38, 321-337 (1997)
Non-Patent Document 6: K. Aika, A. Ohya, A. Ozaki, Y. Inoue, I. Yasumori, Journal of Catalysis, 92, 305-311 (1985)
Non-Patent Document 7: F. Rosowski, A. Hornung, O. Hinrichsen, D. Herein, M. Muhler, G. Ertl, Applied Catalysis A: General, 151, 443-460 (1997)

GB 253 540 A discloses ammonia synthesis by passing a mixture of nitrogen and hydrogen at a relatively low pressure (even atmospheric) and at a temperature of at least 500°C over a mixture of (1) iron, nickel, cobalt, tungsten or mixtures thereof, (2) lithium nitride or amide (Li NH2 or Li2 NH), and (3) alumina, magnesia, lime or mixtures thereof.
GB 199 032 A discloses a catalytic material for ammonia synthesis which comprises a mixture of (1) the nitride or amide of lithium, uranium, calcium, barium, strontium, titanium, glucinum, molybdenum, or vanadium, (2) an inert oxide, such as magnesia or lime, and (3) powdered lead, cadmium, bismuth, antimony, commercial zinc, gold, copper, or silver, which accelerates the decomposition in hydrogen of the nitride or amide. With the exception of zinc, all the metals mentioned under (3) above are prepared by heating the oxides in hydrogen, preferably in the presence of the inert oxide to prevent fusion. Ammonia is obtained by passing a mixture of nitrogen and hydrogen over the catalytic material at a temperature less than 600°C and at atmospheric pressure.
US 2003/065209 A1 discloses a selective hydrogenation process for producing aminonitriles by contacting the corresponding dinitriles with a hydrogen-containing fluid in the presence of a hydrogenation catalyst, a solvent and an amide additive. The catalyst in the process is a hydrogenation catalyst suitable for hydrogenating a dinitrile to an aminonitrile. Preferred are catalysts based on transition metals selected from the group consisting of iron, cobalt, nickel, rhodium and combinations thereof. The catalyst may also contain one or more promoters in addition to the transition metals mentioned above, for example, one or more of Group VIB and Group VII metals such as chromium, molybdenum and tungsten. The catalyst can also be in the form of an alloy, including a solid solution of two or more metals, or an individual metal. The catalytic metal can also be supported on an inorganic support such as alumina, magnesium oxide and combinations thereof. The metal can be supported on an inorganic support. The preferred inorganic support is magnesium oxide, and the preferred supported catalyst is a magnesium oxide supported nickel-iron catalyst.
LAI-PENG Ma et al.: "Catalytically Enhanced Hydrogen Storage Properties of Mg(NH2)2 + 2LiH Material by Graphite-Supported Ru Nanoparticles", J. Phys. Chem. C, 2008, 112 (46), pp 18280-18285, DOI: 10.1021/jp806680n, concerns developing metal-N-H systems as potential hydrogen storage media, by experimentally examining the possibility of N-H bond activation by using metal catalyst. The graphite-supported Ru nanoparticles (Ru/C catalyst) were prepared and their effect was evaluated on the hydrogen storage properties of Mg(NH2)2 + 2LiH material. This article shows that the Ru/C catalyst is catalytically active toward both dehydrogenation and rehydrogenation reactions of Mg(NH2)2 + 2LiH.
US 1 159 364 A discloses a catalyst for the production of ammonia, and teaches that if a gaseous mixture containing nitrogen and hydrogen is suitably passed in contact with a suitable material composed mainly or essentially of nitrogen and an alkali metal such as sodium or potassium, the nitrogen and hydrogen of the gaseous mixture are united to form ammonia. When nitrogen and sodium are used as the catalytic agent, such agent is preferably prepared by suitably passing dry ammonia gas in contact with metallic sodium at a temperature of about 300°C. A pumice stone acts as support for the catalytic agent.
CN 103 977 828 A discloses a catalyst for ammonia synthesis and ammonia decomposition, which is used as a body and/or additive, the body being one or more than two of nitrogen and/or hydrogen-containing compound of a main group element, and the additive comprising one or more selected from support, transition metal nitride or transition metal alloy. Said main group element is one selected from Li, Na, K, Cs, Mg, Ca, Ba and Al. The support is one of Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, SiO2, Al2O3, BN, Si3N4, Mg3N2, Ca3N2, AlN, molecular sieve, carbon material and Metal-Organic Frameworks(MOF). Said transition metal nitride is an IVB, VB, VIB, VIIB or VIIIB group element, such as one nitride of Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Co. Said transition metal alloy is an IVB, VB, VIB, VIIB or VIIIB group element.
US 3 148 157 A discloses a method for the manufacture of catalysts wherein an anhydrous alumina support is impregnated with a catalytic agent selected from the group consisting of alkali metals and alkali metal amides, comprising immersing said support in liquid ammonia during the impregnation thereof with said agent and thereafter evaporating the ammonia.
Summary of the invention
Problem to be Solved by Invention
Two-dimensional electride compounds are conventionally produced from metal nitrides and metals as raw materials. However, in this production method, after mixing these raw materials, reaction at high temperature and for a long time is required. Specifically, taking Ca2N production as an example, Ca2N is obtained by mixing Ca3N2 and Ca metal and heating at 800°C for 100 hours under vacuum conditions (Non-Patent Document 2). That is, extremely severe production conditions are required for production of two-dimensional electride compounds. Therefore, a simpler production method for using the performance of the two-dimensional electride compound is required.
On the other hand, an ammonia synthesis method of the Haber-Bosch method usually requires a high pressure of 20 MPa or more. For this reason, a high-pressure reaction apparatus is required, so that a method for producing ammonia at lower pressure is required. In recent years, an ammonia synthesis method using a supported metal catalyst has been studied, but the performance is still insufficient, and a catalyst capable of reacting at a lower pressure than the Haber-Bosch method is not found.
The inventors of the present invention have found that a catalysis in which a transition metal is supported on a two-dimensional electride compound becomes an ammonia synthesis catalyst having high activity. However, since the two-dimensional electride compound itself is unstable, there is a problem that stability as a catalyst is low. Furthermore, when a two-dimensional electride compound is used as a catalyst support, there is a problem that processability is poor and it is difficult to mold a catalyst according to the reaction. Furthermore, a BET specific surface area when Ca2N was used as a support was measured and found to be about 1m2/g. There was also a problem that when a transition metal is supported, particles of the supported transition metal became large and cannot be supported in high dispersion.
Means for solving the problem
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a composite in which a metal amide compound represented by the general formula (1) (hereinafter sometimes referred to as "metal amide") is supported on a specific support, and then a transition metal as a catalysis metal is further supported on them; and a production method thereof. The present invention has been completed based on the above findings.
That is,
A composite according the invention is as defined in appended claim 1, and comprises ruthenium, a support, and a metal amide compound,
wherein the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, and
the metal amide compound is represented by the formula Ca(NH2)2.
This composite of the invention may have a BET specific surface area of 10 m2/g or more.
A use of this composite according to the invention is as defined in appended claim 3, i.e. as a supported metal catalyst.
A method of producing this composite of the invention is as defined in appended claim 4, and comprises steps of:
mixing a metal atom source comprising a Ca metal atom, the support, and liquid ammonia,
obtaining a metal amide-supporting support mixing by reacting the metal atom source with the liquid ammonia to form the metal amide compound on the support,
supporting a raw material compound of ruthenium on the metal amide-supporting support, and
depositing ruthenium by thermally decomposing the raw material of ruthenium.

According to another aspect of the invention defined in appended claim 5, a use of a composite as a supported metal catalyst specifically in ammonia synthesis, is such that
the composite comprises ruthenium, a support, and a metal amide compound,
the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, or an Al2O3 support, and that
the metal amide compound is represented by the formula Ca(NH2)2.

A method of synthesizing ammonia according to this other aspect of the invention, as defined in appended claim 6, comprises a step of bringing a gas comprising nitrogen and a gas comprising hydrogen into contact with a composite used as an ammonia synthesis catalyst, to synthesize ammonia,
wherein the composite comprises ruthenium, a support, and a metal amide compound,
wherein the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, or an Al2O3 support, and
wherein the metal amide compound is represented by the formula Ca(NH2)2.
According to this method of synthesizing ammonia of the invention, a temperature at which the gas comprising nitrogen and the gas comprising hydrogen are brought into contact with the ammonia synthesis catalyst, is 100°C or more and 600°C or less.
Still according to this method of synthesizing ammonia of the invention, the pressure when contacting the ammonia synthesis catalyst is 10 kPa or more and 20 MPa or less.
Effect of the invention
The composite of the present invention can be produced without requiring high temperature and long-time reaction, and can more easily use the properties of the two-dimensional electride compound. Since the composite of the present invention can be obtained without carrying out a reaction at high temperature and for long time during its production process, it is a composite in which the ruthenium transition metal is supported with high dispersion. Therefore, the composite of the present invention has high performance as a supported metal catalyst, particularly as an ammonia synthesis catalyst.
When the composite of the present invention is used as an ammonia synthesis catalyst, it shows higher catalytic activity than the supported metal catalyst described in Patent Document 11. That is, it is advantageous in that it is possible to produce ammonia with a high reaction efficiency.
When used as an ammonia synthesis catalyst, the composite of the present invention stably produces ammonia even if a reaction is continued for a long time, and the reaction activity hardly decreases. Since a catalyst life is long, it is advantageous in that ammonia can be produced with high production efficiency.
In the method for producing a composite of the present invention, the composite of the present invention can be produced without requiring high temperature and long-time reaction. Therefore, it is possible to obtain a composite in which the ruthenium transition metal is supported with high dispersion, which is advantageous in the production of a supported metal catalyst, particularly an ammonia synthesis catalyst.
In the ammonia synthesis method of the present invention, ammonia can be synthesized with a relatively inexpensive catalyst containing a metal amide compound and a support including an inexpensive metal oxide. By using the composite of the present invention, it is possible to synthesize ammonia with a low reaction pressure. That is, ammonia can be synthesized with high efficiency and with long-term chemical and thermal stability.
When the composite of the present invention is used as a supported metal catalyst, it is possible to be used as a catalyst in various reactions, for example, it is advantageous in that an ammonia decomposition reaction can be promoted.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an example of a composite of the present invention and a production flow of an example of the composite.
FIG. 2 is a TEM photograph of a composite of Ca(NH2)2/ZrO2 in which Ca(NH2)2 is supported on a ZrO2 support.
FIG. 3 is a graph showing catalytic activities when a composite in which different loading amounts of Ca(NH2)2 are supported on a ZrO2 support and Ru is further supported was used as an ammonia synthesis catalyst.
FIG. 4 is a graph showing catalytic activities when a composite in which Ca(NH2)2 is supported on a ZrO2 support and a different loading amount of Ru is further supported was used as an ammonia synthesis catalyst.
FIG. 5 is a graph showing ammonia synthesis rates of each catalysts when the composites of the present invention produced using various supports are used as ammonia synthesis catalysts.
FIG. 6 is a graph showing results of stability evaluation tests on catalysts of Example 1 and Comparative Example 2.
FIG.7 is a graph showing results of ammonia decomposition reactions shown in Example 14, Comparative Example 7 and Comparative Example 8.
Scope of claims [claim1]
1. A composite comprising ruthenium, a support, and a metal amide compound,
wherein the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, and
the metal amide compound is represented by the formula Ca(NH2)2.

[claim2]
2. The composite according to claim 1, wherein the composite has a BET specific surface area of 10 m2/g or more.

[claim3]
3. Use of the composite of claim 1 or 2 as a supported metal catalyst.

[claim4]
4. A method of producing the composite according to claim 1 or 2, comprising steps of:
mixing a metal atom source comprising a Ca metal atom, the support, and liquid ammonia,
obtaining a metal amide-supporting support mixture by reacting the metal atom source with the liquid ammonia to form the metal amide compound on the support,
supporting a raw material compound of ruthenium on the metal amide-supporting support mixture, and
depositing ruthenium by thermally decomposing the raw material of ruthenium.

[claim5]
5. Use of a composite as a supported metal catalyst in ammonia synthesis,
wherein the composite comprises ruthenium, a support, and a metal amide compound,
wherein the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, or an Al2O3 support, and
wherein the metal amide compound is represented by the formula Ca(NH2)2.

[claim6]
6. A method of synthesizing ammonia, comprising a step of bringing a gas comprising nitrogen and a gas comprising hydrogen into contact with a composite used as an ammonia synthesis catalyst, to synthesize ammonia,
wherein the composite comprises ruthenium, a support, and a metal amide compound,
wherein the support is a metal oxide support of at least one metal oxide which is selected from the group consisting of ZrO2, TiO2, CeO2 and MgO, or an Al2O3 support, and
wherein the metal amide compound is represented by the formula Ca(NH2)2.

[claim7]
7. The method for synthesizing ammonia according to claim 6, wherein a temperature at which the gas comprising nitrogen and the gas comprising hydrogen are brought into contact with the ammonia synthesis catalyst, is 100°C or more and 600°C or less.

[claim8]
8. The method for synthesizing ammonia according to claim 6 or 7, wherein the pressure when contacting the ammonia synthesis catalyst is 10 kPa or more and 20 MPa or less.
  • Applicant
  • JAPAN SCIENCE AND TECH AGENCY
  • TOKYO INSTITUTE OF TECHNOLOGY
  • Inventor
  • HOSONO HIDEO
  • HARA MICHIKAZU
  • KITANO MASAAKI
  • YOKOYAMA TOSHIHARU
  • INOUE YASUNORI
IPC(International Patent Classification)
Specified countries Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Please contact us by E-mail or facsimile if you have any interests on this patent.

PAGE TOP

close
close
close
close
close
close