Carbon-based catalyst, for ammonia synthesis, which exhibits high activity under low-pressure and low-temperature conditions, and ammonia synthesis method using same

Abstract

The present invention relates to a promoter-containing catalyst for ammonia synthesis, and an ammonia synthesis method using same. According to the catalyst material of the present invention, and the method for preparing same, ammonia can be highly-efficiently synthesized at a lower temperature and pressure than in the conventional commercial Haber-Bosch process, and thus the present invention has the benefits of significantly reducing the process energy consumption and carbon dioxide emissions.

Description

Carbon-based catalyst for ammonia synthesis showing high activity under low pressure and low temperature conditions and method for synthesizing ammonia using the same

[0001] The present invention relates to a carbon-based catalyst for ammonia synthesis that exhibits high activity under low pressure and low temperature conditions and a method for synthesizing ammonia using the same.

[0002]

[0003] Ammonia is a compound composed of nitrogen and oxygen. Its molecular formula is NH3. It exists as a gas at room temperature with a pungent odor. Small amounts are present in the atmosphere, trace amounts in natural waters, and even in soil, where it is produced by bacteria decomposing nitrogenous organic compounds. Ammonia is used as a raw material in various chemical industries, in the production of ammonia water, and as a solvent for ionic substances.

[0004] The most common method for producing ammonia is the Haber-Bosch process, which synthesizes it from hydrogen and nitrogen. This process is performed at high pressure (over 200 atm) and high temperature (400-500°C) in the presence of an iron or ruthenium catalyst. This reaction consumes a huge amount of energy, approximately 30 GJ / ton NH3, and the fossil fuels used to supply this energy emit a large amount of greenhouse gases equivalent to 1.8 tons CO2 / ton NH3. In addition, catalytic activity can be inhibited due to the competitive nature of nitrogen and hydrogen molecules to adsorb onto the catalyst surface. In addition, nitrogen among the reactants has a very stable triple bond structure, so the ammonia synthesis rate through catalytic reaction is generally only 20%.

[0005] In addition, to achieve the government's target hydrogen supply volume (5.26 million tons / year) by 2040, the government is planning to procure at least 10-50% of the target green hydrogen supply from overseas at low cost from 2030 onwards. However, green hydrogen still has low energy density when pressurized and liquefied for long-distance transport, and hydrogen loss and energy consumption are high during transport, making it difficult to secure price competitiveness. On the other hand, ammonia is evaluated as the most suitable hydrogen storage and transportation medium due to its high hydrogen storage density and easy liquefaction, so technology is needed to convert overseas green hydrogen into ammonia and store and transport it.

[0006] Accordingly, through numerous technological developments and optimization of the Haber-Bosch process, the energy consumption has been reduced to 28 GJ / ton NH3, which is close to the theoretical value. However, in order to reduce the production cost, the energy required for ammonia synthesis must be further reduced, and since existing commercial catalysts are designed to operate under high temperature and high pressure conditions, their ammonia synthesis performance is very low under the low pressure and low temperature conditions we desire, so it is necessary to develop and use a groundbreaking catalyst that can sufficiently synthesize ammonia at much lower pressure (100 atm or less) and temperature (400°C or less) than the existing process conditions (400-500°C, 200 atm or more).

[0007]

[0008] The purpose of the present invention is to provide a novel catalyst material and a method for producing the same, which exhibits a much higher ammonia synthesis rate than existing commercial ammonia synthesis catalysts at lower pressure (less than 100 atm) and lower temperature (400°C) than the existing Haber-Bosch process for producing ammonia.

[0009]

[0010] The present invention provides a catalyst for ammonia synthesis, comprising: a carbon-based support on which a first metal catalyst is supported; and a second metal co-catalyst additionally supported on the carbon-based support on which the first metal catalyst is supported.

[0011] In the ammonia synthesis catalyst of the present invention, the carbon-based support may be selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar, activated carbon, activated carbon fiber, carbon nanotube, and ketchup black, and the carbon-based support may contain 1 to 10 mass% of nitrogen or oxygen relative to the mass of the carbon-based support.

[0012] In the ammonia synthesis catalyst of the present invention, the first metal may be selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), and osmium (Os), and the first metal catalyst may be included in an amount of 1 to 20 mass% relative to the mass of the carbon-based support.

[0013] In the ammonia synthesis catalyst of the present invention, the second metal may be selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), and the second metal cocatalyst may be included in an amount of 0.1 to 3 mmol / g relative to the mass of the carbon-based support.

[0014] The present invention provides a method for synthesizing ammonia at a temperature of 300 to 500°C and a pressure of 10 to 100 atm using the above ammonia synthesis catalyst.

[0015] The present invention provides a method for producing a catalyst for ammonia synthesis, comprising the steps of (a) supporting a first metal catalyst and a second metal cocatalyst on a carbon-based support; and (b) treating the carbon-based support with acid.

[0016] In the method for manufacturing an ammonia synthesis catalyst of the present invention, the carbon-based support may be selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar, activated carbon, activated carbon fiber, carbon nanotube, and ketchup black.

[0017] In the method for manufacturing an ammonia synthesis catalyst of the present invention, the first metal may be selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), and osmium (Os), and the first metal catalyst may be included in an amount of 1 to 20 mass% relative to the mass of the carbon-based support.

[0018] In the method for producing an ammonia synthesis catalyst of the present invention, the second metal may be selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), and the second metal cocatalyst may be included in an amount of 0.1 to 3 mmol / g relative to the mass of the carbon-based support.

[0019] In the method for producing an ammonia synthesis catalyst of the present invention, the acid treatment may be performed using an acid selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid at 20 to 100°C.

[0020]

[0021] According to the catalyst material of the present invention and the method for manufacturing the same, ammonia can be synthesized with high efficiency at lower temperature and pressure than the existing commercial Haber-Bosch process, thereby significantly reducing process energy consumption and carbon dioxide emissions.

[0022]

[0023] Figure 1 is a TEM image of a catalyst for ammonia synthesis according to Example 1 of the present invention.

[0024] Figure 2 is an XRD graph of a catalyst for ammonia synthesis according to Example 5 of the present invention.

[0025]

[0026] The ammonia synthesis catalyst of the present invention will be described in detail with reference to the attached drawings below.

[0027] The drawings presented below are provided as examples to ensure that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the drawings presented below and may be embodied in other forms. The drawings presented below may be exaggerated to clarify the spirit of the present invention.

[0028] At this time, if there is no other definition in the technical and scientific terms used, they have the meaning commonly understood by a person of ordinary skill in the technical field to which this invention belongs, and the description of known functions and configurations that may unnecessarily obscure the gist of the present invention is omitted in the following description and attached drawings.

[0029] Additionally, the singular forms used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0030] In this specification and the appended claims, the terms first, second, etc. are not used in a limiting sense but are used to distinguish one component from another.

[0031] In this specification and the appended claims, the terms “include” or “have” mean that a feature or component described in the specification is present, and unless specifically limited, does not preclude the possibility that one or more other features or components may be added.

[0032] In this specification and the appended claims, when a part such as a film (layer), region, component, etc. is said to be on or above another part, it includes not only the case where it is directly above and in contact with another part, but also the case where another film (layer), another region, another component, etc. is interposed therebetween.

[0033]

[0034] The ammonia synthesis catalyst of the present invention is characterized by comprising: a carbon-based support on which a first metal catalyst is supported; and a second metal co-catalyst additionally supported on the support on which the first metal catalyst is supported.

[0035]

[0036] In one specific example, the carbon-based support may include a one-dimensional carbon-based material or other carbon-based material, and may preferably be selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar derived from natural plants, activated carbon, activated carbon fiber, carbon nanotubes, and ketchup black, and more preferably may include nitrogen-containing carbon black, carbon black, or carbon nanotubes.

[0037] More specifically, the one-dimensional carbon-based material may be one or a combination of two or more selected from the group consisting of carbon nanotubes (CNTs), graphene nanoribbons (GNRs), carbon nanofibers, and carbon nanowires, and the carbon nanotubes may be single-wall carbon nanotubes (SWNTs) or multi-wall carbon nanotubes (MWNTs). Preferably, multi-wall carbon nanotubes may be used as the one-dimensional carbon-based material. Multi-wall carbon nanotubes have superior mechanical strength compared to carbon nanotubes such as single-wall carbon nanotubes, superior structural maintenance properties upon repeated tension, and a wide tensile range, and thus are advantageous in being used as a support.

[0038] In addition, the one-dimensional carbon material may have a diameter of 10 to 200 nm, preferably 20 to 150 nm, and a length of 10 to 100 μm, preferably 20 to 80 μm, but is not limited thereto.

[0039] The above other carbonaceous materials may be one or a combination of two or more selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar, activated carbon, activated carbon fiber, and ketchup black.

[0040] The above carbon-based support may contain 1 to 10 mass% of nitrogen or oxygen relative to the mass of the carbon-based support, preferably 2 to 9 mass%, and more preferably 3 to 8 mass%.

[0041] By using the above carbon-based support, the specific surface area of ​​the carbon-based support increases, so that the metal catalyst can be dispersed in a small and uniform manner, thereby reducing the unit cost of the catalyst, and preventing sintering of the metal catalyst and cocatalyst during long-term use. In addition, by utilizing the high electrical conductivity of the carbon-based support, electrons can be quickly supplied to nitrogen molecules, thereby promoting the nitrogen dissociation step, and since it binds well to the dissociated nitrogen atoms, there is an advantage in that it can promote the step in which the hydrogenation reaction proceeds and ammonia is produced.

[0042]

[0043] In one specific example, a non-limiting example of the first metal may be a metal selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), molybdenum (Mo), and osmium (Os), and preferably ruthenium.

[0044] The first metal catalyst may be included in an amount of 1 to 20 mass% relative to the support mass, preferably 2 to 15 mass%, and most preferably 3 to 8 mass%.

[0045] The average particle diameter of the first metal catalyst may be 0.1 to 50 nm, preferably 0.1 to 20 nm, and most preferably 0.1 to 5 nm. When the first metal catalyst has an average particle diameter within the above range, the reaction sites exposed to the surface area increase, thereby increasing the synthesis performance per unit mass of the first metal, and as the synthesis performance increases, the amount of the first metal used may be reduced, thereby reducing the unit cost of the catalyst.

[0046]

[0047] In one specific example, the second metal may be an alkali metal or an alkaline earth metal, and non-limiting examples of the second metal include a metal selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), and preferably barium.

[0048] The second metal cocatalyst may be included in an amount of 0.1 to 3.0 mmol / g relative to the mass of the support, preferably 0.5 to 2.0 mmol / g, and most preferably 0.7 to 1.5 mmol / g.

[0049] Due to the additional loading of the second metal cocatalyst, there is an advantage in that the nitrogen bonding force is weakened by supplying electrons to nitrogen, which is a reactant of the ammonia synthesis reaction (Lewis base), and the reaction rate of the nitrogen dissociation step (the rate-determining step of the overall reaction) is accelerated, thereby allowing the reaction to proceed in the forward direction.

[0050]

[0051] In one specific example, the average particle diameter of the ammonia synthesis catalyst may be 1 to 1,000 μm, preferably 2 to 900 μm, and most preferably 3 to 800 μm, but is not limited thereto.

[0052] In addition, the specific surface area of ​​the above ammonia synthesis catalyst through BET measurement is 10 to 2,000 m 2 / g may be, preferably 20 to 1,500 m 2 / g may be, most preferably 30 to 1,000 m 2 / g. The ammonia synthesis catalyst having the above average particle size and specific surface area has the advantage that nitrogen molecules can be easily adsorbed on the surface of the catalyst.

[0053]

[0054] The method for synthesizing ammonia using the ammonia synthesis catalyst of the present invention can be carried out at a temperature of 300 to 500°C, and preferably, ammonia can be synthesized at a temperature of 350 to 450°C. In addition, the method can be carried out at a pressure of 10 to 100 atm, and is characterized in that ammonia is synthesized preferably at a pressure of 30 to 80 atm.

[0055] The most common method for producing ammonia is the Haber-Bosch process, which synthesizes ammonia from hydrogen and nitrogen. It is performed at high pressure (over 200 atm) and high temperature (400-500°C) in the presence of a catalyst. This reaction consumes a huge amount of energy, emits a large amount of greenhouse gases, and the catalytic activity can be inhibited due to the competitive nature of nitrogen and hydrogen molecules to adsorb on the catalyst surface. In addition, nitrogen among the reactants has a very stable triple bond structure, so the ammonia synthesis rate through the catalytic reaction is generally only 20%.

[0056] However, the method of synthesizing ammonia using the ammonia synthesis catalyst of the present invention has the effect of significantly reducing process energy consumption and carbon dioxide emissions because it shows a higher ammonia synthesis rate than existing commercial ammonia synthesis catalysts at lower pressure and lower temperature compared to the Haber-Bosch process.

[0057]

[0058] The method for producing an ammonia synthesis catalyst of the present invention may include (a) a step of supporting a first metal catalyst and a second metal cocatalyst on a carbon-based support; and (b) a step of acid-treating the carbon-based support.

[0059] In one specific example, the method for supporting the first metal catalyst may include dissolving the first metal catalyst precursor in a suitable solvent (water, alcohol, acetone, THF, DMF), impregnating the support through a simple wetness impregnation method or a wetness impregnation method, and then drying the solvent and performing a reduction treatment. A vapor deposition method may be used, but there is no particular limitation as long as it is a general supporting method.

[0060] In one specific example, in the method for supporting the first metal catalyst, the first metal may be selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), molybdenum (Mo) and osmium (Os), and preferably may be ruthenium, and at this time, the precursor of the ruthenium catalyst may be ruthenium metal, ruthenium oxide (RuO2; ruthenium oxide), ruthenium red, ruthenium acetylacetonate (Ru(acac)3; ruthenium acetylacetonate), ruthenium chloride (RuCl3; ruthenium chloride), ruthenocene (Bis(cyclopentadienyl) ruthenium), ruthenium nitrosyl nitrate, ruthenium iodide (RuI3; ruthenium iodide), triruthenium dodecacarbonyl (Ru3(CO) 12 ; triruthenium dodecacarbonyl), ruthenium nitrate (Ru(NO3)3; ruthenium nitrate), etc. can be used, but are not limited thereto. At this time, the first metal catalyst may be included in an amount of 1 to 20 mass% relative to the support mass, preferably 2 to 15 mass%, and most preferably 3 to 8 mass%.

[0061] In one specific example, before the step of supporting the first metal catalyst, the first metal catalyst may be additionally pretreated. The pretreatment step is a step of heating and calcining while flowing an inert gas such as nitrogen, argon, helium, or a reducing gas such as ammonia reaction synthesis gas (H2+N2), hydrogen, diluted hydrogen (balance gas: an inert gas such as nitrogen, argon, or hydrogen), carbon monoxide, or diluted carbon monoxide (balance gas: an inert gas such as nitrogen, argon, or hydrogen). The heating temperature varies depending on the component of the first metal, but is preferably heated to 250 to 700°C.

[0062]

[0063] In one specific example, the method for supporting the second metal promoter may include dissolving the second metal promoter precursor in a suitable solvent (water, alcohol, acetone, THF, DMF), impregnating the support with a simple wetness impregnation method (incipient wetness impregnation), and then drying the solvent and performing a reduction treatment. A vapor deposition method may also be used, but there is no particular limitation as long as it is a general supporting method.

[0064] In one specific example, in the method for supporting the second metal promoter, the second metal may be selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba), and preferably barium, and at this time, the barium promoter precursor may be barium nitrate (Ba(NO3)2; barium nitrate), barium hydroxide (Ba(OH)2; barium hydroxide), barium perchlorate (Ba(ClO4)2; barium perchlorate), barium isopropoxide (Ba(OCH(CH3)2)2; barium isopropoxide), barium fluoride (BaF2; barium fluoride), barium oxide (BaO; barium oxide), barium bromide (BaBr2; barium bromide), Barium chloride (BaCl2; barium chloride), barium iodide (BaI2; barium iodide), barium acetate (Ba(CH3COO)2; barium acetate), barium carbonate (BaCO3; barium carbonate), barium sulfate (BaSO4; barium sulfate), etc. can be used, but are not limited thereto. At this time, the second metal promoter can be included in an amount of 0.1 to 3.0 mmol / g relative to the mass of the support, preferably 0.5 to 2.0 mmol / g, and most preferably 0.7 to 1.5 mmol / g.

[0065] In one specific example, before the step of supporting the second metal promoter, the second metal promoter may be additionally pretreated. The pretreatment step is a step of heating and calcining while flowing a reducing gas such as an inert gas such as nitrogen, argon, or helium, or an ammonia reaction synthesis gas (H2+N2), hydrogen, diluted hydrogen (balance gas: an inert gas such as nitrogen, argon, or hydrogen), carbon monoxide, or diluted carbon monoxide (balance gas: an inert gas such as nitrogen, argon, or hydrogen). The heating temperature varies depending on the component of the first metal, but is preferably heated to 250 to 700°C.

[0066]

[0067] In one specific example, the acid treatment in step (b) may use a strong acid at 20 to 100°C, preferably an acid selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid. At this time, the concentration of the strong acid may be 0.05 to 1.0 M, preferably 0.1 to 0.9 M, and more preferably 0.3 to 0.8 M. When a strong acid having a concentration in the above range is used, impurities remaining on the catalyst surface can be removed without damaging the catalyst itself, and there is an advantage of increasing the degree of dispersion.

[0068]

[0069] The present invention is described in detail below through examples. However, these examples are provided for the purpose of explaining the present invention in more detail, and the scope of the present invention is not limited by the following examples.

[0070]

[0071] <Example 1> Preparation of a catalyst for ammonia synthesis

[0072] 0.27 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) is completely dissolved in 3 mL of water, and 2 g of carbon black is added to prepare a slurry. The slurry containing the ruthenium chloride and carbon black is left in the air at a temperature between room temperature and 50°C for 20 minutes, and then a solution of 0.54 g of barium nitrate (Ba(NO3)2) dissolved in 2 mL of distilled water is mixed. After that, the slurry is left at room temperature for 20 minutes, dried in an oven at 100°C for 15 hours, and then acid-treated in a 0.6 M sulfuric acid solution to prepare the final catalyst.

[0073]

[0074] <Example 2> Preparation of a catalyst with a ruthenium content of 9 wt%

[0075] The catalyst for ammonia synthesis was prepared using the same method as that of Example 1, except that 0.486 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) was used instead of 0.27 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru).

[0076]

[0077] <Example 3> Preparation of a catalyst with a ruthenium content of 3 wt%

[0078] The catalyst for ammonia synthesis prepared in Example 1 was prepared in the same manner as that prepared in Example 1, except that 0.16 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) was used instead of 0.27 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) and 0.27 g of barium nitrate (Ba(NO3)2) was mixed instead of 0.54 g of barium nitrate (Ba(NO3)2).

[0079]

[0080] <Example 4> Preparation of a catalyst having a barium content of 0.5 mmol / g

[0081] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that 0.27 g of barium nitrate (Ba(NO3)2) was used instead of 0.54 g of barium nitrate (Ba(NO3)2).

[0082]

[0083] <Example 5> Preparation of a catalyst having a barium content of 2.0 mmol / g

[0084] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that 1.08 g of barium nitrate (Ba(NO3)2) was used instead of 0.54 g of barium nitrate (Ba(NO3)2).

[0085]

[0086] <Example 6> Preparation of a biochar-supported catalyst using soybean stover as a raw material

[0087] The catalyst for ammonia synthesis was manufactured using the same manufacturing method as that of Example 1, except that biochar manufactured from soybeans was used as a support instead of carbon black.

[0088]

[0089] <Example 7> Preparation of a carbon black support catalyst with added nitrogen

[0090] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that carbon black doped with 2 wt% nitrogen was used as a support instead of the existing carbon black.

[0091]

[0092] <Example 8> Preparation of a catalyst using carbon nanotubes as a support

[0093] 0.069 g of ruthenium chloride precursor (RuCl3·xH2O, 38% Ru) is completely dissolved in 2 mL of acetone, and 0.5 g of carbon nanotubes are added to prepare a slurry. The slurry is left in the air at room temperature to 50°C for 12 hours to remove the solvent, and then transferred to a kiln and heat-treated at 200°C for 2 hours while flowing hydrogen. Thereafter, the temperature is increased to 350°C while flowing nitrogen gas, and heat-treated for 3 hours. After the heat-treated powder is impregnated with a solution of 0.14 g of barium nitrate (Ba(NO3)2) dissolved in 2 mL of distilled water, and then exposed to the air in the same manner to remove the solvent. The final catalyst was prepared by acid treatment of the powder in a 0.6 M sulfuric acid solution.

[0094]

[0095] <Comparative Example 1> Preparation of a catalyst not containing ruthenium

[0096] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that the ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) was not used.

[0097]

[0098] <Comparative Example 2> Preparation of a catalyst not containing barium

[0099] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that barium nitrate (Ba(NO3)2) was not used.

[0100]

[0101] <Comparative Example 3> Preparation of a catalyst with a ruthenium content of 2 wt%

[0102] The catalyst for ammonia synthesis was prepared using the same method as that of Example 1, except that 0.108 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru) was used instead of 0.27 g of ruthenium chloride precursor (RuCl3·xH2O, 37% Ru).

[0103]

[0104] <Comparative Example 4> Preparation of a catalyst containing cesium as a cocatalyst

[0105] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that cesium nitrate (CsNO3) was used instead of barium nitrate (Ba(NO3)2).

[0106]

[0107] <Comparative Example 5> Preparation of a catalyst containing potassium as a cocatalyst

[0108] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that potassium nitrate (KNO3) was used instead of barium nitrate (Ba(NO3)2).

[0109]

[0110] <Comparative Example 6> Preparation of a catalyst using MgO as a support

[0111] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that an MgO series support (silica) was used instead of carbon black.

[0112]

[0113] <Comparative Example 7> Preparation of a catalyst using CeO2 as a support

[0114] It was manufactured using the same manufacturing method as the ammonia synthesis catalyst manufactured in Example 1, except that a CeO2 series support (ceria) was used instead of carbon black.

[0115]

[0116] <Experimental Example 1> Structural Analysis of a Catalyst for Ammonia Synthesis

[0117] First, the structure of the ammonia synthesis catalyst manufactured through the manufacturing method of Example 1 was observed using a transmission electron microscope (TEM).

[0118] Referring to Figure 1, it can be seen that the catalyst and cocatalyst components are finely dispersed.

[0119]

[0120] Next, the structure of the ammonia synthesis catalyst manufactured through the manufacturing method of Example 5 was observed through X-ray diffraction analysis.

[0121] Referring to Figure 2, only the diffraction peaks due to the carbon nanotube and co-catalyst components were analyzed, and no diffraction peaks for the ruthenium catalyst component were observed, which means that the catalyst component was highly dispersed in very small amounts.

[0122]

[0123] <Experimental Example 2> Analysis of ammonia synthesis rate using ammonia synthesis catalyst

[0124] After synthesizing ammonia using the catalysts synthesized through the manufacturing methods of Examples 1 to 5 and Comparative Examples 1 to 7, the ammonia synthesis rate was evaluated. A mixed gas of H2 / N2=3 (molar ratio) was injected top-down into a high-pressure gas phase fixed bed reactor. The reaction was carried out at 50 atm and 400°C, and 5,000 h -1 The reaction was carried out at a reaction flow rate (GHSV), and the results are shown in Table 1.

[0125]

[0126] Catalyst componentCatalyst content (wt%)Promoter componentPromoter content (mmol / g)Support typeAmmonia synthesis rate (g-NH3 / g-cat·hr)Example 1Ru5Ba1Carbon black1.0Example 2Ru9Ba1Carbon black0.92Example 3Ru3Ba0.5Carbon black1.0Example 4Ru5Ba0.5Carbon black0.65Example 5Ru5Ba2Carbon black0.85Example 6Ru5Ba1Soybean stalk biochar0.8Example 7Ru5Ba1Nitrogen-doped carbon black1.2Example 8Ru5Ba1Carbon nanotube1.35Comparative example 1Ru0Ba1Carbon black~0Comparative example 2Ru5Ba0Carbon black0.12Comparative example 3Ru2Ba1Carbon black0.25Comparative example 4Ru5Cs1Carbon Black 0.3Comparative Example 5Ru5K1Carbon Black 0.2Comparative Example 6Ru5Ba1MgO 0.8Comparative Example 7Ru5Ba1 CeO2 0.25

[0127] Referring to Table 1 above, when ammonia was synthesized using the catalysts (support type: carbon-based material, first metal catalyst component: Ru, second metal promoter component: Ba) manufactured through the manufacturing methods of Examples 1 to 5, it was found that the ammonia synthesis rate was very excellent compared to the catalysts manufactured through the manufacturing methods of Comparative Examples 1 to 7. In particular, in the case of catalysts containing 3 to 8 wt% of the first metal catalyst and 0.7 to 1.5 mol / g of the second metal promoter (Examples 1, 2, and 5), an ammonia synthesis rate of about 0.85 g-NH3 / g-cat·hr or more was shown. In general, when an ammonia synthesis rate of 0.3 g-NH3 / g-cat·hr or more is shown, it can be seen that it is at a higher level than the performance of existing commercial catalysts under the same low pressure conditions, and therefore, it was found that the ammonia synthesis rate was very excellent.

[0128] In comparison, it was found that in the case of a catalyst that did not include a first metal catalyst, such as Comparative Example 1, or did not include a second metal co-catalyst, such as Comparative Example 2, hardly any ammonia was synthesized under the conditions of 50 atm and 400°C.

[0129] In addition, in the case of a catalyst having a different content of the first metal catalyst, such as Comparative Example 3, it was confirmed that the ammonia synthesis rate was significantly lower compared to the catalysts of Examples 1 and 2.

[0130] In addition, it was confirmed that the ammonia synthesis rate significantly decreased even when the components of the cocatalyst were different, as in Comparative Examples 4 and 5, or when the types of the support were different, as in Comparative Examples 6 and 7. In particular, it was confirmed that the ammonia synthesis rate increased when a carbon-based support, such as carbon black or carbon nanotubes, was used compared to when MgO was used as the support, as in Comparative Example 6.

[0131]

[0132] As described above, the ammonia synthesis catalyst according to the present invention exhibits an excellent ammonia synthesis rate even under low temperature and low pressure conditions, unlike the ammonia synthesis according to the general Haber-Bosch method, by using a specific support, catalyst, and cocatalyst.

Claims

1. A carbon-based support on which a first metal catalyst is supported; and A catalyst for ammonia synthesis, wherein a second metal cocatalyst is additionally supported on a carbon-based support on which the first metal catalyst is supported.

2. In paragraph 1, A catalyst for ammonia synthesis, wherein the carbon-based support is selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar, activated carbon, activated carbon fiber, carbon nanotube, and ketchup black.

3. In paragraph 1, A catalyst for ammonia synthesis, wherein the carbon-based support contains 1 to 10 mass% of nitrogen or oxygen relative to the mass of the carbon-based support.

4. In paragraph 1, A catalyst for ammonia synthesis, wherein the first metal is selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), and osmium (Os).

5. In paragraph 1, A catalyst for ammonia synthesis, wherein the first metal catalyst is included in an amount of 1 to 20 mass% relative to the mass of the carbon-based support.

6. In paragraph 1, A catalyst for ammonia synthesis, wherein the second metal is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

7. In paragraph 1, A catalyst for ammonia synthesis, wherein the second metal cocatalyst is included in an amount of 0.1 to 3 mmol / g relative to the mass of the carbon-based support.

8. A method for synthesizing ammonia at a temperature of 300 to 500°C and a pressure of 10 to 100 atm using an ammonia synthesis catalyst according to any one of claims 1 to 7. 9.(a) a step of supporting a first metal catalyst and a second metal cocatalyst on a carbon-based support; and (b) A method for producing a catalyst for ammonia synthesis, comprising the step of acid-treating the carbon-based support.

10. In paragraph 9, A catalyst for ammonia synthesis, wherein the carbon-based support is selected from the group consisting of low-grade coal, carbon black, nanocellulose, biochar, activated carbon, activated carbon fiber, carbon nanotube, and ketchup black.

11. In paragraph 9, A method for producing a catalyst for ammonia synthesis, wherein the first metal is selected from the group consisting of iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), and osmium (Os).

12. In paragraph 9, A method for producing a catalyst for ammonia synthesis, wherein the first metal catalyst is included in an amount of 1 to 20 mass% relative to the mass of the carbon-based support.

13. In paragraph 9, A method for producing a catalyst for ammonia synthesis, wherein the second metal is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba).

14. In paragraph 9, A method for producing a catalyst for ammonia synthesis, wherein the second metal cocatalyst is included in an amount of 0.1 to 3 mmol / g relative to the mass of the carbon-based support.

15. In paragraph 9, A method for producing a catalyst for ammonia synthesis, wherein the above acid treatment is performed at a temperature of 20 to 100°C using an acid selected from the group consisting of sulfuric acid, hydrochloric acid, and nitric acid.

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