KR20160142135A - Catalysts for ammonia dehydrogenation, methods of producing the same, and methods of producing hydrogen gas from ammonia using the same - Google Patents

Abstract

Provided is a catalyst for ammonia dehydrogenation, containing ruthenium (Ru), nitrogen (N), and carbon (C) and has a bond between ruthenium (Ru) and nitrogen (N) and a bone between nitrogen (N) and carbon (C). The nitrogen (N) provides electron density to ruthenium (Ru) metal, thereby a catalyst containing the same for ammonia dehydrogenation shows high ammonia conversion rate and high stability to temperature. Also, nitrogen (N) enhances thermal stability of the catalyst and improves durability.

Description

FIELD OF THE INVENTION The present invention relates to a catalyst for ammonia dehydrogenation, a process for producing the same, and a method for producing hydrogen from ammonia using the same. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for ammonia dehydrogenation,

The present invention relates to a catalyst for ammonia dehydrogenation, a process for producing the same, and a process for producing hydrogen from ammonia using the same. More particularly, the present invention relates to a process for the preparation thereof having improved activity and durability and a process for producing hydrogen from ammonia using the process.

To address the need for clean, sustainable technology for the development of portable, automotive and / or stationary fuel cells, potentially feasible hydrogen storage materials have become a rapidly growing field in research for the last decade. Examples of such materials include metal hydrides, metal-organic frameworks and chemical hydrates. Particularly, chemical hydrogen storage materials such as sodium borohydride and ammonia borane are capable of storing hydrogen in a safe manner, and the most active research among these materials is underway. In addition, liquid and / or solid materials such as formaic acid, ammonia (NH ₃ ) and the like are also of interest as chemical hydrogen storage materials applicable to fuel cells because they are used in field power production This is because they offer economical hydrogen storage and transportation methods.

On the other hand, NH _{3, which} is a gas that can be condensed under mild conditions (20 ° C and 0.8 MPa), has a very high hydrogen storage density of 17.8 wt% and can produce hydrogen from ammonia when a suitable catalyst is used There is great interest as a carrier of hydrogen. In addition, H ₂ produced from NH ₃ can directly supply the product to polymer electrolyte membrane fuel cells (PEMFCs) without generating CO. This is a potential advantage over conventional hydrocarbon reforming systems that require expensive and externally exposed hydrogen purification systems. Moreover, the fuel used in the ammonia dehydrogenation process can easily be regenerated with NH ₃ by a harber-bosch process.

In order to be in the fuel cell field, NH ₃ is useful, although, efficient adsorbent remaining even when reducing the amount of ammonia to less than 200ppb, unreacted NH ₃ is possible to suppress the poisoning of the PEMFC catalyst of NH ₃ complete in due to A conversion (> 99%) is required. In order to achieve such a high conversion rate, a high reaction temperature (> 400 DEG C) is generally required to overcome a high activation barrier.

On the other hand, various Ru-based heterogeneous catalysts such as Ru / carbon nanotube (CNT), Ru / Al ₂ O ₃ and the like are being studied to promote the ammonia dehydrogenation reaction. In particular, Ru catalysts on carbon-based supports such as CNTs and carbon nanofibers (CNFs) are known to exhibit high activity in this reaction. The activity of Ru / CNT and Ru / CNF can be improved by increasing the charge density of the carbon support through nitrogen doping or the like. Recently, a catalyst containing iron (Fe), nitrogen (N) and carbon (C) for oxygen reduction reaction (hereinafter referred to as Fe-NC catalyst) has been developed in addition to a catalyst for decomposing ammonia The Fe-NC catalyst has a number of Fe-NC contacts. In such a nanostructure, the introduced nitrogen atom is made to impart an electron density to the Fe-center metal, which ultimately can improve the ORR activity.

KR10-2012-0010960A

Embodiments of the present invention provide a catalyst for ammonia dehydrogenation which is excellent in catalytic activity and exhibits long-term stability.

Other embodiments of the present invention provide a process for preparing a catalyst for ammonia dehydration which can be mass-produced at an economical cost.

In another embodiment of the present invention, there is provided a method for producing hydrogen from ammonia using the catalyst for ammonia dehydration, wherein the method produces hydrogen having a high ammonia conversion.

In one embodiment of the present invention, the catalyst for ammonia dehydrogenation comprises ruthenium (Ru), nitrogen (N) and carbon (C), wherein the ruthenium (Ru) And nitrogen (N), and a combination of nitrogen (N) and carbon (C).

In an exemplary embodiment, the catalyst for ammonia dehydrogenation comprises 0.1 to 20 parts by weight of the ruthenium (Ru), 0 to 63 parts by weight of the nitrogen (N), and the carbon ( C) 0.01 to 100 parts by weight.

In an exemplary embodiment, the nitrogen (N) may be doped to the carbon (C) and the ruthenium (Ru).

In an exemplary embodiment, the nitrogen (N) may enhance the electron density of the ruthenium (Ru).

In an exemplary embodiment, the ammonia conversion can range from 50 to 99.9% at a temperature ranging from 450 to 570 占 폚.

In an exemplary embodiment, it may exhibit an ammonia conversion of 95 to 99.9% at a temperature in the range of 500 to 550 占 폚.

In another embodiment of the present invention, there is provided a process for preparing a mixture comprising: a first step of mixing a ruthenium (Ru) precursor, a carbon (C) precursor and a nitrogen (N) precursor in a solvent to form a mixture; A second step of heat treating and drying the mixture to form a solid product; And a third step of reducing the solid product to form a catalyst for ammonia dehydration comprising ruthenium (Ru) metal, nitrogen (N) and carbon (C).

In an exemplary embodiment, the ruthenium (Ru) precursor is selected from ruthenium chloride (RuCl ₃ ), ruthenium acetylacetonate (Ru (acac) ₃ ), ruthenium (III) chloride hydrate (RuCl ₃ .xH ₂ O) Id (RuI _3), ruthenium (IV) oxide hydrate (RuO ₂ and xH ₂ O), ruthenium (III) bromide (RuBr _3), and hexahydro ammin ruthenium (II) chloride _{([Ru (NH 3) 6} ] Cl 2) ≪ RTI ID = 0.0 > and / or < / RTI >

In an exemplary embodiment, the carbon (C) precursor is selected from the group consisting of carbon black, graphene oxide, reduced graphene oxide, single wall carbon nanotubes, double wall carbon nanotubes, and multiwalled carbon nanotubes. Or more.

In an exemplary embodiment, the nitrogen (N) precursor is selected from the group consisting of dicyanamide, dimethyl cyanamide, diethylcyanamide, benzyl (methyl) cyanamide, and Benzyl cyanamide, and the like.

In an exemplary embodiment, in the first step, a chelate compound comprising a bond of ruthenium (Ru) ions and nitrogen (N) is formed, and in the second step, the chelate compound Can be fixed.

In an exemplary embodiment, in the second step, the nitrogen (N) of the chelate compound may be one that prevents aggregation of the ruthenium (Ru) ions.

In an exemplary embodiment, the second step may be conducted at a temperature in the range of 500 to 550 DEG C for 3 to 5 hours.

In an exemplary embodiment, the third step may be conducted at a temperature in the range of 450 to 650 ° C for 1 to 2 hours.

In another embodiment of the present invention, there is provided a process for producing hydrogen from ammonia using the catalyst for ammonia dehydration.

The catalyst for ammonia dehydrogenation according to an embodiment of the present invention has excellent catalytic activity and can exhibit long-term stability.

According to the method for producing a catalyst for ammonia dehydration according to an embodiment of the present invention, a large amount of a catalyst for ammonia dehydration can be produced at an economical cost.

According to the method of producing hydrogen from ammonia using the catalyst for ammonia dehydrogenase according to an embodiment of the present invention, high ammonia conversion can be exhibited and stability can be shown even at a high temperature and a long time.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a method for producing a catalyst for ammonia dehydrogenation produced according to an embodiment of the present invention. FIG.
FIG. 2 is a transmission electron microscope (TEM) image of a catalyst for ammonia dehydration prepared according to an embodiment of the present invention and a catalyst for ammonia dehydration prepared according to a comparative example.
FIG. 3 is a high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) photograph of a catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention.
4 is an energy-dispersive X-ray (EDX) graph of a catalyst for ammonia dehydration prepared according to one embodiment of the present invention.
FIG. 5 is a graph showing X-ray diffraction (XRD) of the catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention and the catalyst for ammonia dehydration prepared according to the comparative example.
6 is a graph showing the results of thermogravimetric analysis (TGA) of the catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention and the catalyst for ammonia dehydration prepared according to the comparative example.
FIG. 7 is a graph showing the X-ray photoelectron spectroscopy (XPS) measurement results of the catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention (C1s: (a), Ru3p: (b)).
FIG. 8 is a graph showing XPS measurement results of the catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention and the catalyst for ammonia dehydration prepared according to the comparative example.
9 is a graph showing the results of XPS measurement of a catalyst for ammonia dehydrogenation produced according to one embodiment of the present invention (C1s: (a), N1s (b), Ru3p: (c)).
10 is a graph showing the ammonia conversion according to the temperature of the catalyst for ammonia dehydration prepared according to one embodiment of the present invention and the catalyst for ammonia dehydration prepared according to the comparative example.
11 is a graph showing the ammonia conversion according to the gas hourly space velocity (GHSV) of ammonia in a dehydrogenation reaction using a catalyst for ammonia dehydration prepared according to one embodiment of the present invention.
12 is a graph showing the results of an experiment on the long-term stability of ammonia dehydrogenation of a catalyst for ammonia dehydrogenation prepared according to one embodiment of the present invention.
13 is a graph showing the results of an experiment on the long-term stability of the catalyst for ammonia dehydration prepared according to one embodiment of the present invention and the catalyst for ammonia dehydration prepared according to the comparative example.
14 is a HAADF-STEM photograph of the ammonia dehydrogenation catalyst prepared according to Comparative Example after ammonia dehydrogenation reaction.
15 is an EDX spectrum after the reaction of the catalyst for ammonia dehydration prepared according to the comparative example.

As used herein, the term "Ru-NC catalyst" refers to a catalyst containing ruthenium (Ru), nitrogen (N), and carbon (C), and includes ruthenium (Ru) (N) and a combination of nitrogen (N) and carbon (C).

As used herein, the term " Ru-C catalyst " means a catalyst containing ruthenium (Ru) and carbon (C) and containing a combination of ruthenium (Ru) and carbon (C).

As used herein, the term " CN catalyst " means a catalyst containing carbon (C) and nitrogen (N), and includes a combination of nitrogen (N) and carbon (C).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention.

Catalyst for ammonia dehydration

The present invention relates to a catalyst for ammonia dehydrogenation which comprises ruthenium (Ru), nitrogen (N) and carbon (C), and is characterized in that the ruthenium (Ru) And a combination of nitrogen (N) and carbon (C). The present invention also provides a catalyst for ammonia dehydrogenation.

In an exemplary embodiment, the catalyst for ammonia dehydration may be a carbonation product obtained by heat treating a mixture comprising a ruthenium (Ru) precursor, a nitrogen (N) precursor and a carbon (C) precursor.

(R), nitrogen (N), and carbon (C) are represented by Ru, N, and C, respectively, and the ruthenium (Ru) precursor, Precursor and C precursor.

In an exemplary embodiment, the Ru precursor may be at least one selected from the group consisting of an organic compound containing Ru ions and an inorganic compound, and specifically includes ruthenium chloride (RuCl ₃ ), ruthenium acetylacetonate (Ru (acac) ₃ ), ruthenium (III) chloride hydrate (RuCl ₃ and xH ₂ O), and ruthenium iodide (RuI _3), ruthenium (IV) oxide hydrate (RuO ₂ and xH ₂ O), ruthenium (III) bromide (RuBr ₃₎ , And hexammin ruthenium (II) chloride ([Ru (NH ₃ ) ₆ ] Cl ₂ ), and preferably the Ru precursor is at least one selected from the group consisting of ruthenium (III) chloride hydrate or ruthenium acetylacetonate (Ru (acac) ₃ ).

In an exemplary embodiment, the N precursor may be at least one selected from the group consisting of various organic compounds including CN bonds, including amides. Specifically, for example, the N precursor may be selected from the group consisting of dicyanamide, And may be at least one selected from the group consisting of dimethyl cyanamide, diethylcyanamide, benzyl (methyl) cyanamide, benzyl cyanamide, and the like.

In an exemplary embodiment, the C precursor may be at least one selected from the group consisting of carbon black, graphene oxide, reduced graphene oxide, single wall carbon nanotubes, double wall carbon nanotubes, multiwall carbon nanotubes, .

In an exemplary embodiment, the catalyst for ammonia dehydration comprises about 0.1 to 20 parts by weight of Ru, 0.01 to 63 parts by weight of N, and 0.01 to 100 parts by weight of C, based on the total weight of the catalyst for ammonia dehydration, . More preferably, 0.5 to 5 parts by weight of Ru, 10 to 20 parts by weight of N and 80 to 90 parts by weight of C may be contained.

When the Ru content is 5 parts by weight or more, Ru metal can be sintered. When the N content is 20 parts by weight or more, the site of interaction between the ammonia and the Ru active site can be reduced. When the C content is 90 parts by weight or more, The reactivity of the reaction may be reduced.

On the other hand, if Ru is less than 0.5 part by weight, ammonia dehydrogenation reaction rate may be lowered. If N is less than 10 parts by weight, the reactivity improving effect may be lowered due to decrease of interaction. , The reactivity may be lowered due to the reduction of the surface area.

In an exemplary embodiment, C may function as a catalyst support. In addition, the catalyst support may have a hollow structure.

In an exemplary embodiment, Ru is bonded to N, and N may be bonded to C. That is, the catalyst for ammonia dehydration may include a Ru-NC bond in which Ru, N and C are sequentially bonded.

In an exemplary embodiment, the N may provide an electron density to the Ru. Accordingly, the activity of the catalyst for ammonia dehydration can be increased.

In an exemplary embodiment, the use of ammonia dehydration catalyst may exhibit a BET specific surface area value of about 700 to 1200 m ² · g ^-1, more particularly from about 800 m ² · g ^-1 to about 1000 m ² · g ^-1 . ≪ / RTI >

In an exemplary embodiment, the ammonia dehydrogenation catalyst may exhibit an ammonia conversion in the range of about 95 to 99.9%.

In an exemplary embodiment, the catalyst for ammonia dehydration may exhibit an ammonia conversion in the range of from about 50 to about 99.9% at a temperature in the range of from about 450 to about 570 < 0 > C, Ammonia conversion of 99.9%.

In forming the catalyst for ammonia dehydration according to an embodiment of the present invention, the N precursor fixes the Ru precursor to prevent aggregation between the Ru precursors and prevent sintering. Thus, Ru particles of a small size can be formed. In an exemplary embodiment, the Ru may have a size of about 1.0 to 1.5 nm, and more specifically about 1.25 to 1.35 nm.

Further, in the catalyst for ammonia dehydration according to an embodiment of the present invention, N may provide electrons to Ru. Specifically, electrons can be provided to the active region of Ru among the catalysts for ammonia dehydrogenation. Accordingly, the electron density of the active region of Ru can be increased, the catalytic activity of the catalyst for ammonia dehydrogenase including the Ru can be improved, and thermal stability and durability can be improved.

Preparation method of Ru-N-C catalyst

The catalyst for ammonia dehydrogenation including ruthenium (Ru), nitrogen (N) and carbon (C) according to the present invention may be prepared by the following process. That is, a method for preparing a catalyst for ammonia dehydration of the present invention comprises a first step of mixing a ruthenium (Ru) precursor, a carbon (C) precursor and a nitrogen (N) precursor in a solvent to form a mixture; A second step of heat treating and drying the mixture to form a solid product; And a third step of reducing the solid product to form a catalyst for ammonia dehydration.

(R), nitrogen (N), and carbon (C) are represented by Ru, N, and C, respectively, and the ruthenium (Ru) precursor, Precursor and C precursor.

First, a Ru precursor, a C precursor, and an N precursor are mixed to form a mixture (Step 1).

In an exemplary embodiment, the Ru precursor may be at least one selected from the group consisting of an organic compound containing Ru ions and an inorganic compound, and specifically includes ruthenium chloride (RuCl ₃ ), ruthenium acetylacetonate (Ru (acac) ₃ ), ruthenium (III) chloride hydrate (RuCl ₃ and xH ₂ O), and ruthenium iodide (RuI _3), ruthenium (IV) oxide hydrate (RuO ₂ and xH ₂ O), ruthenium (III) bromide (RuBr ₃₎ , And hexammin ruthenium (II) chloride ([Ru (NH ₃ ) ₆ ] Cl ₂ ), and preferably the Ru precursor is at least one selected from the group consisting of ruthenium (III) chloride hydrate or ruthenium acetylacetonate (Ru (acac) ₃ ).

In an exemplary embodiment, the N precursor may be at least one selected from the group consisting of various organic compounds including amide and a bond of carbon (C) with nitrogen (N) (hereinafter, CN bond) For example, the N precursor may be selected from the group consisting of dicyanamide, dimethyl cyanamide, diethylcyanamide, benzyl (methyl) cyanamide, benzyl cyanamide, And the like.

In an exemplary embodiment, the C precursor may be at least one selected from the group consisting of carbon black, graphene oxide, reduced graphene oxide, single wall carbon nanotubes, double wall carbon nanotubes, multiwall carbon nanotubes, .

In an exemplary embodiment, the mixture may be formed in a polar solvent, and specifically includes water, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dimethylformamide , DMF), and the like.

In an exemplary embodiment, the Ru precursor, C precursor, and N precursor may each be included in a ratio of about 0.5 to 5 parts by weight: 80 to 90 parts by weight: 10 to 20 parts by weight, respectively.

In an exemplary embodiment Ru metal can be sintered when Ru of the Ru precursor is greater than or equal to 5 parts by weight and when the N of the N precursor is greater than or equal to 20 parts by weight the interaction site of the Ru active site capable of reacting with ammonia is reduced If the C content of the C precursor is 90 parts by weight or more, the reactivity of the ammonia dehydrogenation reaction may be reduced.

On the other hand, if Ru of the Ru precursor is less than 0.5 part by weight, the rate of ammonia dehydrogenation reaction may decrease. If N of the N precursor is less than 10 parts by weight, the reactivity of the ammonia dehydrogenation reaction And if C of the C precursor is 80 parts by weight or less, the reactivity of the ammonia dehydrogenation reaction may be lowered due to a decrease in the surface area of the catalyst for ammonia dehydration.

In an exemplary embodiment, within the mixture, the Ru precursor and C precursor can react to form a Ru-C precursor that includes a combination of Ru ions and C. In addition, within the mixture, the Ru precursor and the N precursor may react to form a Ru-N precursor including a combination of Ru ion and N. Also, at this time, one or more C and / or N may be bonded to the Ru ion to form the Ru-C precursor or Ru-N precursor. As the Ru-C precursor and the Ru-N precursor are formed, the mixture may be formed to include a chelated compound of Ru ion.

The mixture is then heat treated and dried to give a solid product (second step).

In an exemplary embodiment, the Ru-N precursor may be formed by fixing a Ru-N precursor on the C precursor, which is a carbon support, by heat treating and drying the Ru-ion chelate compound contained in the mixture. Accordingly, N of the N precursor may be doped on the C precursor, and Ru ions combined with the N may be uniformly disposed on the carbon support. That is, as the second step is performed, a solid product comprising Ru-N-C precursors including a combination of N and C and a combination of Ru ion and N may be formed. The Ru-N-C precursor also includes Ru-N-C precursors including N and C bonds and Ru ion and N bonds, so that the Ru-N-C precursor may also be a chelate compound.

In an exemplary embodiment, cohesion between the Ru ions of the Ru-N precursor may be inhibited due to N of the Ru-N precursor immobilized on the C precursor, and Ru ions may be formed uniformly and widely dispersed on the carbon support .

In an exemplary embodiment, the second step may be performed at a temperature in the range of 500 to 550 < 0 > C. When the reaction is carried out at a temperature of 500 ° C or lower, the bond between the Ru ion, N and C can be weakened, and when the reaction is carried out at a temperature of 550 ° C or higher, the Ru-N-C catalyst as a final product can be easily decomposed.

In an exemplary embodiment, the second step may be carried out for 3 to 5 hours. If the reaction is conducted for 3 hours or less, the bond between the Ru ion, N and C elements may not be formed sufficiently strong, and if the reaction is carried out at a temperature of 5 hours or more, the Ru-NC catalyst as a final product may be decomposed.

Thereafter, the solid product may be reduced to form a catalyst for ammonia dehydration (Step 3).

Specifically, the Ru-N-C precursor, which is a chelate compound of Ru ions, can be reduced in an inert atmosphere to form Ru metal, a catalyst for ammonia dehydrogenation including N and C (i.e. Ru-N-C catalyst).

In an exemplary embodiment, the catalyst for ammonia dehydration may comprise a combination of a Ru metal and N and a combination of N and C. In addition, it may further include a bond of a Ru metal and C.

In an exemplary embodiment, H ₂ gas or the like may be injected to reduce the solid product, and N ₂ gas or the like may be injected to form an inert atmosphere.

In an exemplary embodiment, the third step may be performed at a temperature in the range of 450 to 650 < 0 > C. When performed at 450 캜 or below, sufficient reduction of Ru ions may not be achieved, and when performed at 650 캜 or higher, reduced Ru metal may be sintered.

In an exemplary embodiment, the third step may be conducted for about 1 to 2 hours. Ru ions may not be sufficiently reduced when carried out for 1 hour or less, and Ru metal may be sintered for 2 hours or more.

As described above, the catalyst for ammonia dehydrogenation including Ru metal, C and N according to an embodiment of the present invention includes a first step of mixing a Ru precursor, C precursor and N precursor to form a mixture; A second step of heat treating and drying the mixture to form a solid product; And a third step of reducing the solid product to prepare a catalyst for ammonia dehydrogenation including Ru metal, C and N. [

Alternatively, after forming a catalyst containing Ru metal and C, dehydrogenation reaction using ammonia is performed, and N generated from the dehydrogenation reaction of ammonia with Ru and C is doped to form Ru metal, C and N The catalyst for ammonia dehydrogenation may be formed.

In general, Ru precursors, N precursors, and C precursors can be purchased at low cost. Accordingly, when a catalyst for ammonia dehydration containing Ru metal, C and N is formed using the Ru precursor, N precursor, C precursor, or the like, it is possible to produce a catalyst for ammonia dehydration at an economical cost, It can be produced in large quantities. Thus, the production unit cost of the process can be reduced.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is to be understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Example 1 (Ru-N-C catalyst)

0.25 g of RuCl ₃ XH ₂ O (Sigma-Aldrich), 1.0 g of carbon black (Ketjen) and 1.0 g of diacinamide (Sigma-Aldrich) were mixed with 50 ml of purified water. Thereafter, heat was applied at 100 DEG C for 4 hours and vigorously stirred to evaporate the water to complete the drying of the mixture to form a black solid. Thereafter, the black solid was ground and pyrolyzed at 550 ° C for 4 hours under N ₂ atmosphere to obtain Ru-NC catalyst, which is the final product of black powder.

At this time, the amount of Ru in the Ru-NC catalyst was about 0.97 wt%. The Ru content was measured using an inductively coupled plasma photo emission spectrometry (ICP-OES).

Comparative Example 1 (Ru-C catalyst) and 2 (C-N catalyst)

In Example 1, the Ru-C catalyst of Comparative Example 1 was synthesized by conducting experiments under the same conditions except that the diacinamide was not used. At this time, the amount of Ru in the Ru-C catalyst was about 0.86 wt%.

Further, in Example 1, CN catalyst according to Comparative Example 2 was synthesized by conducting experiments under the same conditions except that RuCl ₃ XH ₂ O was not used.

Experiments on ammonia dehydrogenation using catalysts according to Example 1 and Comparative Examples 1 and 2

The performance of the catalyst according to Example 1 and Comparative Examples 1 and 2 was measured using a fixed-bed quartz reactor at a flow rate of 37.2 mL min ^-1 at 10% NH ₃ / N ₂ at atmospheric pressure Respectively.

Specifically, the catalyst (? 0.1 g, 0.05g, 0.03g , 0.01g; 100 150 μm) were fixed in the reactor, the H ₂ / N ₂ and 50% for one hour at 550 ° C 30 mL · min ^{- 1 &lt}; / RTI > Thereafter, the reduced catalyst was washed with N ₂ for 1 hour. NH ₃ dehydrogenation reaction was then carried out. The composition of the exhaust gases in each experiment was determined by an on-line chromatograph (Agilent 7890A) equipped with an online gas Porapak Q packed column and molecular sieve capillary columns and a thermal conductivity detector (TCD) Respectively. The amount of unreacted NH ₃ was analyzed using a variable diode laser ammonia gas analyzer (Model Airwell + 7, KINSCO Technology). The activity of the catalyst was monitored by monitoring as a function of GHSV and temperature of ammonia.

Experimental Example 1: Identification of structure and structure of each catalyst

The Ru-N-C catalyst prepared according to Example 1 and the Ru-C catalyst prepared according to Comparative Example 1 were measured and shown in FIGS. 2 to 5 and Table 1.

Types of catalyst BET surface area
(m ₂ · g ^-1 ) Pore size
(nm) Pore volume
(cm ³ · g ^-1 ) Ru-N-C catalyst 898 4.7 1.05 Ru-C catalyst 1,110 5.4 1.57

2 is TEM photographs of Ru-N-C catalyst prepared according to Example 1 and Ru-C catalyst prepared according to Comparative Example 1. FIG. 3 is a HAADF-STEM photograph of the Ru-N-C catalyst prepared according to Example 1. Fig. 4 is an EDX graph of a Ru-N-C catalyst prepared according to Example 1. FIG. 5 is an XRD graph of Ru-N-C catalyst prepared according to Example 1 and Ru-C catalyst prepared according to Comparative Example 1. FIG.

2, it was confirmed that the Ru-N-C catalyst formed a hollow graphite structure even without a sacrificial template, which is useful for reducing chemical substances because it does not require various process steps through various templates.

On the other hand, it was confirmed that the Ru-C catalyst also had a hollow structure, but it was confirmed that Ru was aggregated to a size of about 20 nm. From this, it was confirmed that cyanamide, which is a precursor containing nitrogen, is easy to uniformly disperse Ru during thermal decomposition. Also, it can be seen from this that Fe promotes the formation of hollow carbon nanostructures, and Ru also promotes the formation of hollow N-doped carbon nanostructures during the pyrolysis process of precursors containing carbon and / or nitrogen there was.

 2 to 4, it was confirmed that Ru, C and N were widely dispersed in the catalyst. Referring to FIG. 5, it can be seen that the Ru-NC and Ru-C catalysts exhibit a broad peak around 25.2 ° Which is attributed to the amorphous nature of the carbon sphere.

A broad peak region centered at 42.2 ° corresponding to the Ru metal was derived from the EDX results of the Ru-NC catalyst (see FIG. 4), confirming that the Ru nanoparticles had a size of 1.3 nm as calculated by the Scherrer equation I could. On the other hand, in the spectrum of the Ru-C catalyst, it was confirmed that sharp peaks were formed around the centers of 38.5 °, 44.2 °, 58.5 °, 69.7 °, 78.7 ° and 86.3 ° in addition to the Ru (see black in FIG. 5) . In addition, the average size of the Ru particles in the Ru-C catalyst was about 5.1 nm as calculated by Scherrer's equation, and therefore, it is judged to be larger than the size of the Ru particles in the Ru-N-C catalyst. The results were confirmed to be the same as those observed with TEM.

On the other hand, the external characteristics of the Ru-NC catalyst and the Ru-C catalyst were observed from N ₂ adsorption-desorption isotherms.

Considering table 1, the BET surface area of the NC-Ru catalyst is 898 m ² · g ^- a ^1, showed a BET surface area of lower than 1,110 m ² · g ^-1 of Ru-C catalyst, and, Ru- It was confirmed that the pore size and pore volume of the NC catalyst were slightly small.

Experimental Example 2: Thermal Stability Experiment

The thermal stability of the Ru-N-C catalyst prepared according to Example 1 and the Ru-C catalyst prepared according to Comparative Example 1 were tested and shown in FIG.

6 is a graph showing the TGA results of the Ru-N-C catalyst prepared according to Example 1 and the Ru-C catalyst prepared according to Comparative Example 1, prepared according to one embodiment of the present invention.

6, it was confirmed that the Ru-N-C catalyst showed a stable value up to 500 ° C, and thereafter the mass was abruptly decreased (FIG. 6, red mark). In FIG. 6, it is considered that the decrease of the mass at 100 ° C or less is attributable to the desorption of adsorbed water from the catalyst surface, and the rapid decrease after 500 ° C is considered to be due to the decomposition of the C-N support structure.

On the other hand, the decomposition of Ru-C catalyst started after about 380 ° C. It can be seen that as the temperature is raised, the mass is reduced, which is believed to be due to the decomposition of the hollow carbon structure (see black in FIG. 6).

Thus, it was confirmed that the doped N increased the thermal stability of the catalyst, and thus it is considered that N can contribute to the catalytic activity in the Ru-NC catalyst.

Experimental Example 3: Confirmation experiment of electron density

In order to confirm the electronic states of the elements in the Ru-N-C catalyst prepared according to Example 1 and the Ru-C catalyst prepared according to Comparative Example 1, they were respectively measured by XPS and shown in FIGS.

7 is a graph (C1s: (a), Ru3p: (b)) showing the results of XPS measurement of the Ru-C catalyst prepared according to Example 1 and FIG. 8 is a graph 9 is a graph (C1s: (a), N1s (b), Ru3p: (c)) showing the XPS measurement result of the Ru-NC catalyst prepared according to Example 1

The deconvoluted C 1s XPS spectrum of the Ru-C catalyst showed a narrow Sp2 graphite peak centered at 284.6 eV. An additional peak for the CO bond was identified at 284? 290 eV, presumably due to adsorbed oxygen from the precursor used. In the deconvoluted spectrum of the Ru-C catalyst, it was confirmed that Ru 3p showed a dominant peak around 463.3 eV, which is attributed to RuO ₂ . In addition, referring to FIG. 8, it was confirmed that the 466.1 eV peak was RuO ₂ .xH ₂ O, and that the Ru 3d catalyst showed a single peak around 281.2 eV

On the other hand, in the XPS spectrum of the Ru-N-C catalyst, a narrow SP2 carbon peak was identified centered at 284.6 ev, and an additional peak for C-O bond was identified at 284 to 290 eV. However, it is judged that this is due to C (sp2) -N and C (sp3) -N, which is different from the Ru-C catalyst, and it is judged that nitrogen atoms are introduced into the graphite structure by pyrolysis.

9, the Ru-NC catalyst showed a predominant N1s peak in the range of binding energies of 396 to 408 eV (see Fig. 9b), and pyridinium-nitrile-pyrrolidine- and / or graphite And a graphitic-like nitrogen species. In addition, the Ru 3 P XPS spectrum of the Ru-NC catalyst showed a predominant peak centered at 462.7 eV (see FIG. 9C), wherein a peak of 462.7 eV of the Ru-NC catalyst exhibited lower binding than Ru-C , Which is believed to be due to the fact that the combined nitrogen source provided electron density in the Ru active region. The Ru-NC catalyst also showed a broad peak at 466.6 eV, which is believed to be due to RuO ₂ · xH ₂ O. In addition, as in the Ru 3P spectrum of FIG. 8, it is judged that the Ru 3d peak of Ru-NC is due to the binding energy (281.0 eV) slightly lower than the peak of Ru-C (see FIG. 8d) , It was once again confirmed that electrons are transferred from N to Ru.

Thus, although the surface area of the Ru-NC catalyst is smaller than that of the Ru-C catalyst, the doped nitrogen increases the electron density of Ru, thereby improving the activity and durability of the Ru-NC catalyst as a catalyst in the NH ₃ dehydrogenation reaction I could confirm.

Experimental Example 4: Determination of Ammonia Conversion by Temperature

The ammonia dehydrogenation reaction was carried out using the Ru-N-C catalyst prepared according to Example 1, the Ru-C catalyst prepared according to Comparative Example 1, and the C-N catalyst prepared according to Comparative Example 2

Thereafter, the ammonia conversion rate (?) In the case of using the Ru-NC catalyst in the ammonia dehydrogenation reaction, the ammonia conversion rate (?) In the case of using Ru-C catalyst and the ammonia conversion rate And this is shown in FIG. Particularly, Table 2 shows the ammonia conversion ratio when the Ru-N-C catalyst is used and the ammonia conversion ratio (%) when the Ru-C catalyst is used.

Temperature (℃) C-N catalyst Ru-C catalyst Ru-N-C catalyst 475 0(%) 0(%) 24 (%) 500 0(%) 20 (%) 56 (%) 550 0(%) 68 (%) 95 (%)

10 is a graph showing the ammonia conversion rates of Ru-N-C catalyst prepared according to Example 1, Ru-C catalyst prepared according to Comparative Example 1, and C-N catalyst according to temperature.

10 and Table 2, it was confirmed that when the Ru-N-C catalyst was used, the Ru-C catalyst exhibited excellent activity at a temperature in the range of about 475 to 550 ° C. Specifically, when Ru-NC catalyst at about 550 ° C was used, it showed 95% ammonia conversion and showed much better catalytic activity than Ru-C catalyst with 68% conversion. When Ru-NC catalyst was used, it showed 56% ammonia conversion and showed better catalytic activity than Ru-C catalyst with 24% conversion. Also, it was confirmed that the C-N catalyst exhibited negligible ammonia dehydrogenation activity at a temperature of 600 ° C or lower.

On the other hand, as shown in Table 2, in the case of the Ru-NC catalyst and the Ru-C catalyst, the ammonia conversion increased with increasing temperature, which is considered to be due to the endothermic characteristic of the dehydrogenation process.

Experimental Example 5: Measurement of Ammonia Conversion Rate According to GHSV

Using the Ru-NC catalyst prepared according to Example 1, ammonia had the following gas hourly space velocity (GHSV) values, and the temperatures were 400 ° C., 450 ° C., 550 ° C. and 550 ° C. ▼) were measured and shown in FIG. 11 and Table 3.

GHSV (mL · g ^-1 · h ^-1) 400 ° C 450 ℃ 500 ℃ 550 ℃ 2,234 0 44.7 97.7 99.7 4,469 0 27.8 86.8 99.2 7,448 0 0 55.9 94.5 11,172 0 0 31.2 81.5

11 is a graph showing the ammonia conversion according to GHSV values prepared according to one embodiment of the present invention.

11 and Table 3, the ammonia conversion using Ru-N-C catalyst decreased with increasing GHSV at all temperatures.

Specifically, about 550 ℃ temperature and GHSV of about 2,234 mL · g ^-1 · h ^-1 and compared with the ammonia conversion rate (> 99%) of the Ru-catalyst when the NC, GHSV of about 7,448 mL · g ^-1 · H ^-1 , the ammonia conversion was reduced to about 94.5%. At this time, when the GHSV was further increased to 11,172 mL · g ^-1 · h ^-1 at 550 ° C., it was confirmed that the Ru-NC catalyst still showed an excellent ammonia conversion of 81.5%.

However, at about 450 ° C and 500 ° C, it was confirmed that the NH ₃ conversion was remarkably decreased with the increase of GHSV when Ru-NC catalyst was used.

Specifically, the GHSV was at 450 ℃ 2,234 mL · g ^-1 · h ^-1 ammonia conversion factor of the catalyst when the Ru-NC is reduced to 45% at the same temperature, the GHSV 7,448 mL · g ^-1 · h ^{- 1} , it decreased to 0%. Similarly, the ammonia conversion (98%) of the Ru-NC catalyst under the conditions of 500 ° C and GHSV of 2,234 mL · g ^-1 · h ^-1 was about 31% when GHSV was 11,172 mL · g ^-1 · h ^-1 , Respectively.

In general, as the GHSV of ammonia increases, the residence time of the reactants is shortened and the conversion of ammonia decreases. In contrast, the Ru-NC catalyst prepared according to Example 1 exhibited a high ammonia conversion rate of 81% or more even when the GHSV value of ammonia was high, indicating excellent performance.

Experimental Example 6: Long-term stability measurement of dehydrogenation reaction

The ammonia dehydrogenation reaction was carried out over time using the Ru-NC catalyst prepared according to Example 1 and is shown in FIG. At this time, the GHSV of the Ru-NC catalyst was maintained at 7,448 mL · g ^-1 · h ^-1 and the temperature was maintained at about 550 ° C.

The ammonia dehydrogenation reaction was performed over time using Ru-NC catalyst prepared according to Example 1 and Ru-C catalyst prepared according to Comparative Example 1, and the results are shown in FIG. At this time, the GHSV of ammonia was maintained at 7,448 mL · g ^-1 · h ^-1 and the temperature was maintained at about 550 ° C. The ammonia conversion (red) in the case of using the Ru-NC catalyst in the ammonia dehydrogenation reaction and the ammonia conversion (black) in the case of using the Ru-C catalyst were measured as a function of time and are shown in FIG. 13 .

Also, HAADF-STEM and EDX spectra of the Ru-C catalyst were measured and shown in FIGS. 14 and 15. FIG.

12, when the Ru-N-C catalyst was used at about 550 ° C., the conversion rate of the initial ammonia was 95%, but it decreased to 88% after about 80 hours.

Also, as shown in FIG. 13, when the Ru-NC catalyst was used at about 500 ° C, the conversion rate of the initial NH ₃ was 79%, but it decreased to 61% after about 80 hours.

On the other hand, surprisingly, under the same conditions, when the Ru-C catalyst was used, the conversion rate of the initial ammonia showed a value of 19%, and it was confirmed that it increased to 35% after about 80 hours. That is, it was confirmed that as the time increases, the catalyst activity increases. At this point, the active growth of the Ru-C catalyst is used and the NH ₃ nitrogen dopant according to the N- doped due to the dehydrogenation of Ru-C catalyst converts the nitrogen is combined of Ru-C catalyst (i.e., NH ₃ The same as the Ru-NC catalyst formed) is formed.

Figure 14 is a photograph of HAADF-STEM images taken during the dehydrogenation reaction of Ru-C catalyst NH ₃ prepared according to one embodiment of the present invention, Figure 15 shows Ru-C And the EDX spectrum measured during dehydrogenation reaction of NH ₃ of the catalyst.

14 and 15, when the element of the Ru-C catalyst was randomly measured in four different regions, it was confirmed that the amount of N element in the Ru-C catalyst showed an average amount of 0.82 wt%. It is considered that this is because the nitrogen element binds to the Ru-C catalyst during the dehydrogenation reaction of NH ₃ , and the resultant Ru-NC catalyst is proved to be useful for a long-term operating fuel cell.

Claims (15)

As a catalyst for ammonia dehydration,
Ruthenium (Ru), nitrogen (N), and carbon (C)
The catalyst for ammonia dehydration comprising the combination of ruthenium (Ru) with carbon (C), the ruthenium (Ru) with nitrogen (N), and the nitrogen (N) with carbon (C). The method according to claim 1,
The catalyst for ammonia dehydrogenation comprises 0.1 to 20 parts by weight of ruthenium (Ru), 0.01 to 63 parts by weight of nitrogen (N) and 0.01 to 100 parts by weight of carbon (C) as elemental ratios with respect to the total weight of the catalyst for ammonia dehydration Containing ammonia dehydration catalyst. The method according to claim 1,
Wherein the nitrogen (N) is doped in the carbon (C) and the ruthenium (Ru). The method of claim 3,
Wherein the nitrogen (N) improves the electron density of the ruthenium (Ru). The method according to claim 1,
A catalyst for ammonia dehydration which exhibits an ammonia conversion in the range of 50 to 99.9% at a temperature in the range of 450 to 570 占 폚. 6. The method of claim 5,
A catalyst for ammonia dehydration which exhibits an ammonia conversion of 95 to 99.9% at a temperature in the range of 500 to 550 占 폚. A first step of mixing a ruthenium (Ru) precursor, a carbon (C) precursor and a nitrogen (N) precursor in a solvent to form a mixture;
A second step of heat treating and drying the mixture to form a solid product; And
And a third step of reducing the solid product to form a catalyst for ammonia dehydrogenation including ruthenium (Ru) metal, nitrogen (N), and carbon (C). 8. The method of claim 7,
The ruthenium (Ru) precursor is ruthenium chloride (RuCl _3), ruthenium acetylacetonate (Ru (acac) _3), ruthenium (III) chloride hydrate (RuCl ₃ and xH ₂ O), ruthenium iodide (RuI _3), ruthenium (IV) oxide hydrate (RuO ₂ and xH ₂ O), ruthenium (III) bromide (RuBr _3), and hexahydro ammin ruthenium (II) chloride, one selected from the group consisting of _{([Ru (NH 3) 6} ] Cl 2) By weight based on the total weight of the catalyst for ammonia dehydration. 8. The method of claim 7,
Wherein the carbon (C) precursor is selected from the group consisting of carbon black, graphene oxide, reduced graphene oxide, single wall carbon nanotubes, double wall carbon nanotubes, and multiwalled carbon nanotubes. (2). 8. The method of claim 7,
The nitrogen (N) precursor may be selected from the group consisting of dicyanamide, dimethyl cyanamide, diethylcyanamide, benzyl (methyl) cyanamide, and benzyl cyanamide ). ≪ / RTI > A method for producing a catalyst for ammonia dehydrogenation comprising the steps of: 8. The method of claim 7,
In the first step, a chelate compound comprising a bond of ruthenium (Ru) ion and nitrogen (N) is formed,
Wherein the chelate compound is immobilized on the carbon (C) precursor in the second step. 12. The method of claim 11,
Wherein the nitrogen (N) of the chelate compound prevents agglomeration of the ruthenium (Ru) ions in the second step. 8. The method of claim 7,
Wherein the second step is carried out at a temperature in the range of 500 to 550 DEG C for 3 to 5 hours. 8. The method of claim 7,
Wherein the third step is carried out at a temperature in the range of 450 to 650 ° C for 1 to 2 hours. A process for producing hydrogen from ammonia using the catalyst for ammonia dehydration according to claim 1.

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