Pellet-shaped precursor for preparing ammonia synthesis catalyst, ammonia synthesis catalyst prepared therefrom, and ammonia synthesis method using same

Abstract

The present disclosure relates to a precursor for preparing an ammonia synthesis catalyst, the precursor being pellet-shaped particles containing molybdenum (Mo), cobalt (Co), and iron (Fe), wherein the ratio (I26.5° / I28.5°) of the intensity (I26.5°) of a third peak at 2θ=26.5±0.2° to the intensity (I28.5°) of a fourth peak at 2θ=28.5±0.2° is 0.4 or more as a result of X-ray diffraction (XRD) analysis. An ammonia synthesis catalyst prepared from the precursor enables a fast ammonia synthesis rate, and thus ammonia can be produced with high efficiency under low temperature and low pressure conditions using even a small amount of the catalyst.

Description

Precursor for manufacturing ammonia synthesis catalyst in pellet form, ammonia synthesis catalyst manufactured therefrom, and ammonia synthesis method using the same

[0001] The present disclosure relates to a precursor for preparing a pellet-shaped ammonia synthesis catalyst, an ammonia synthesis catalyst prepared therefrom, and a method for synthesizing ammonia using the same.

[0002] Ammonia is recognized as a crucial medium for providing a stable food supply for humanity and is considered a promising source of future energy. Currently, renewable energy via electricity is difficult to transport and store, so research is underway to convert hydrogen generated from solar and wind energy into ammonia. This method is expected to provide a renewable energy solution, enabling easy transport and storage similar to petroleum products.

[0003] In particular, ammonia has a density 1.5 times that of liquid hydrogen, making it possible to build infrastructure with relatively high density and low cost. This allows ammonia to have a relatively low manufacturing cost. Furthermore, the existing ammonia supply chain can be utilized to supply hydrogen, and it can be used directly as energy in the power generation sector without the need for dehydrogenation to extract hydrogen. Therefore, efficiently controlling ammonia synthesis and decomposition reactions can accelerate the era of carbon-free energy.

[0004] However, conventional ammonia synthesis relies on the Haber-Bosch process, which requires high temperatures and pressures, resulting in extremely high energy consumption. While new processes, such as electrochemical processes, are being proposed for lower costs and greater energy efficiency, research is needed to effectively utilize existing process equipment to improve energy efficiency. This approach involves novel catalyst-based methods for synthesizing ammonia at low temperatures (below 500°C) and pressures (1 to 100 bar). To achieve this, the development of catalysts with high production efficiency is essential.

[0005] Representative active metals known for ammonia synthesis or decomposition include iron (Fe) and ruthenium (Ru), but they have not yet produced satisfactory results. In addition, ruthenium has the problem of low commerciality due to its high cost, so there is an urgent need to develop a catalyst that is more economical and efficient than the existing one.

[0006] The purpose of the present disclosure is to solve the problems of the above-mentioned prior art, and to provide a precursor for producing an ammonia synthesis catalyst comprising three or more components with excellent commerciality.

[0007] Another object of the present disclosure is to provide a method for preparing a precursor for preparing an ammonia synthesis catalyst that can be uniformly prepared with a specific bonding structure that significantly improves ammonia synthesis efficiency.

[0008] Another object of the present disclosure is to provide an ammonia synthesis catalyst having significantly improved ammonia synthesis efficiency at low temperature and low pressure and an ammonia synthesis method using the same.

[0009] The precursor for manufacturing an ammonia synthesis catalyst of the present disclosure is a particle having a pellet shape containing molybdenum (Mo), cobalt (Co) and iron (Fe), and as a result of X-ray diffraction (XRD) analysis, the fourth peak intensity (I) at 2θ = 28.5 ± 0.2° 28.5°) for the third peak intensity (I) at 2θ=26.5±0.2° 26.5° ) of the rain (I 26.5° / I 28.5° ) is 0.4 or higher.

[0010] In one example, the precursor is (Co 1-x Fe x )Mo1O4(0 <x<1)로 표시되는 것일 수 있다.

[0011] In one example, x may be 0.05 to 0.18.

[0012] In one example, the precursor further comprises cesium (Cs), (Co 1-x Fe x Cs z )Mo1O4(0 <x<1, 0.01≤z≤0.1)로 표시되는 것일 수 있다.

[0013] In one example, z / x can be between 0.3 and 1.0.

[0014] In one example, the X-ray diffraction (XRD) analysis results may show a first peak at 2θ=14.5±0.2°, a second peak at 2θ=25.5±0.2°, a fifth peak at 2θ=32.7±0.2°, and a sixth peak at 2θ=44.0±0.2°.

[0015] The ammonia synthesis catalyst of the present disclosure is prepared from the precursor for preparing the ammonia synthesis catalyst described above.

[0016] In one example, the catalyst is (Co 1-x Fe x )Mo1N y (0 <x<1, 0.2<y<0.4)로 표시될 수 있다.

[0017] In one example, the catalyst is (Co 1-x Fe x Cs z )Mo1N y (0 <x<1, 0.2<y<0.4, 0.01≤z≤0.1)로 표시되는 것일 수 있다.

[0018] In one example, the X-ray diffraction (XRD) analysis results may show a first peak at 2θ=32.5±0.2°, a second peak at 2θ=35.5±0.2°, a third peak at 2θ=40.0±0.2°, a fourth peak at 2θ=42.5±0.2°, and a fifth peak at 2θ=47.0±0.2°.

[0019] In one example, the catalyst may be a pellet having an average particle diameter of 0.1 mm to 10 mm.

[0020] In one example, the catalyst may include a plurality of pores.

[0021] In one example, among the total pore volume of the catalyst, the volume occupied by pores having a pore size of 10 nm or more may be 95% or more.

[0022] The present disclosure includes a method for producing the ammonia synthesis catalyst described above.

[0023] The method for manufacturing an ammonia synthesis catalyst of the present disclosure includes a step of manufacturing a precursor for manufacturing an ammonia synthesis catalyst in a pellet shape; and an ammonolysis step of manufacturing an ammonia synthesis catalyst by heat-treating the precursor for manufacturing an ammonia synthesis catalyst in an ammonia atmosphere.

[0024] In one example, the step of manufacturing a precursor for manufacturing an ammonia synthesis catalyst in the form of a pellet may include: (S10) introducing a molybdenum precursor and a cobalt precursor; (S20) introducing a C3-10 organic acid; (S30) introducing an iron precursor to manufacture a precursor solution; (S40) heating the precursor solution to manufacture a precursor powder for manufacturing an ammonia synthesis catalyst; and (S50) molding the precursor powder.

[0025] In one example, the molar ratio of the iron precursor to the total moles of the iron precursor and cobalt precursor may be 0.05 to 0.3.

[0026] In one example, the method may further include a step of introducing a cesium (Cs) precursor into the precursor solution after the step (S30) and before the step (S40).

[0027] In one example, the molar ratio of the cesium precursor to the total moles of the iron precursor and the cesium precursor may be 0.05 to 0.1.

[0028] In one example, the step of introducing the cesium (Cs) precursor can be performed by a co-precipitation method.

[0029] In one example, the method may further include a step of adding polyalcohol to the precursor solution after the step (S30) and before the step (S40).

[0030] In one example, the molar ratio of the polyhydric alcohol to the organic acid may be 0.1 to 2.0.

[0031] In one example, the step (S30) may be performed by a co-precipitation method.

[0032] In one example, the ammonolysis step may be performed by heating the precursor for preparing the ammonia synthesis catalyst at a temperature of 400°C to 800°C in an ammonia atmosphere.

[0033] The present disclosure includes a method for synthesizing ammonia using the ammonia synthesis catalyst described above.

[0034] In one example, it may be performed under temperature conditions of 500°C or less.

[0035] In one example, it may be performed under pressure conditions of 50 bar or less.

[0036] In one example, the ammonia synthesis rate is 17 mmol / gcat ·h can be more than that.

[0037] The precursor for manufacturing an ammonia synthesis catalyst of the present invention is manufactured according to a specific manufacturing method, so that the ratio of a specific peak in X-ray diffraction (XRD) analysis can be satisfactorily 0.4 or more, and thus a high-efficiency quaternary catalyst can be manufactured. The ammonia synthesis catalyst manufactured from the precursor can have a fast ammonia synthesis rate, and thus ammonia can be manufactured with high efficiency even with a small amount of catalyst.

[0038] Figures 1 and 3 are XRD analysis spectra of precursor powders for manufacturing an ammonia synthesis catalyst according to an example.

[0039] Figure 2 is a schematic diagram illustrating the esterification reaction between an organic acid and a polyhydric alcohol.

[0040] Figure 4 is an XRD analysis spectrum of an ammonia synthesis catalyst according to an example.

[0041] Figure 5 is a BJH curve of an ammonia synthesis catalyst according to an example.

[0042] The precursor for producing a pellet-shaped ammonia synthesis catalyst of the present disclosure, the ammonia synthesis catalyst produced therefrom, and the ammonia synthesis method using the same are described in detail. The terms used in this specification have been selected from widely used general terms as much as possible while considering the functions of the present disclosure. However, these terms may vary depending on the intentions of engineers working in the relevant field, precedents, the emergence of new technologies, etc. Unless otherwise defined, the technical and scientific terms used may have the meaning commonly understood by those of ordinary skill in the technical field to which this invention pertains.

[0043] 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.

[0044] In this specification and the appended claims, the terms first, second, etc. are not used in a limiting sense but are used for the purpose of distinguishing one component from another.

[0045] As used herein and in the appended claims, the singular expression "singular" includes the plural expression unless the context clearly dictates otherwise. Furthermore, the plural expression "singular" includes the singular expression unless the context clearly dictates otherwise.

[0046] Additionally, the numerical ranges used herein include lower and upper limits and all values ​​within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of upper and lower limits of numerical ranges defined in different shapes. Unless otherwise specifically defined in the specification of the present disclosure, values ​​outside the numerical range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0047] The term "about" or the like used in this specification and the appended claims is used to encompass the tolerance when an tolerance exists.

[0048] The present disclosure provides a precursor for preparing an ammonia synthesis catalyst containing molybdenum (Mo), cobalt (Co), and iron (Fe) and having a pellet shape. In this case, the precursor is an oxide for preparing an ammonia synthesis catalyst, which will be described later, and the precursor according to one embodiment exhibits characteristics that are different from the prior art in the X-ray diffraction (XRD) analysis results of the oxide. As a result of the X-ray diffraction (XRD) analysis, the precursor exhibits a fourth peak intensity (I) at 2θ=28.5±0.2°. 28.5° ) for the third peak intensity (I) at 2θ=26.5±0.2° 26.5° ) of the rain (I 26.5° / I 28.5° ) may be 0.4 or greater, 0.5 or greater, or 0.6 or greater, and advantageously 1.0 or greater, 2.0 or greater, or 3.0 or greater, and even better 4.0 or greater, or 5.0 or greater. The upper limit is not particularly limited, but may be 10.0 or less.

[0049] When the above range is satisfied, an ammonia synthesis catalyst having the properties targeted in the present invention can be manufactured. When the above range is exceeded, in particular, I 26.5° / I 28.5° If it is less than 0.4, it is not preferable because the properties aimed at in the present invention cannot be achieved.

[0050] In one embodiment, the X-ray diffraction (XRD) analysis result of the precursor may show a first peak at 2θ=14.5±0.2°, a second peak at 2θ=25.5±0.2°, a third peak at 2θ=26.5±0.2°, a fourth peak at 2θ=28.5±0.2°, a fifth peak at 2θ=32.7±0.2°, and a sixth peak at 2θ=44.0±0.2°, as shown in FIG. 1.

[0051] When manufacturing precursors using conventional technology, the metal components are not synthesized in the same ratio as they were added, but rather a structure (Co) is formed in a specific ratio. 0.7 Fe 0.3Mo1O4) is formed, which has a low ammonia synthesis efficiency, so it is desirable to minimize the formation of the structure. At the same time, in order to manufacture the catalyst aimed at in the present invention, it is desirable to introduce Fe while maintaining the CoMoO4 structure, so that a precursor can be obtained while maintaining the introduced ratio. Here, Co 0.7 Fe 0.3 The representative peak corresponding to Mo1O4 is the fourth peak, and the peak corresponding to CoMoO4 is the third peak, and therefore, Co 0.7 Fe 0.3 I which stands for Mo1O4 28.5° I, which means CoMoO4 with low peak intensity 26.5° The higher the peak intensity, the more desirable it is. In particular, as in the present invention, the fourth peak intensity (I 28.5° ) for the third peak intensity (I 26.5° ) of the rain (I 26.5° / I 28.5° ) When a catalyst is manufactured using a precursor that satisfies a specific range, the effect of significantly improving ammonia synthesis efficiency can be realized.

[0052] Furthermore, since the precursor has a pellet shape, the pore structure of the catalyst manufactured using it can be developed, thereby improving the pore volume and specific surface area. This allows for the realization of an ammonia synthesis catalyst with a significantly improved ammonia synthesis rate even at low temperatures and pressures.

[0053] In one embodiment, the precursor may have an average particle size of 0.1 mm to 10 mm, 0.15 mm to 8 mm, 0.2 mm to 5 mm, 0.3 mm to 2 mm, or 0.5 mm to 1.5 mm. When the above range is satisfied, a catalyst manufactured therefrom may exhibit excellent specific surface area characteristics, thereby enhancing catalytic activity.

[0054] In one embodiment, the precursor is (Co 1-x Fe x)Mo1O4(0 <x<1)로 표시되는 것일 수 있다. 이때 x는 0.01 내지 0.9, 0.01 내지 0.7, 0.05 내지 0.5, 0.05 내지 0.18 또는 0.07 내지 0.15일 수 있다. 상기 만족하는 전구체로 촉매를 제조한 경우, 우수한 암모니아 합성 속도 향상의 효과를 구현할 수 있다. 또한 후술하는 전구체의 제조방법에 있어서, 상기 1-x는 투입하는 코발트 전구체의 몰비, x는 투입하는 철 전구체의 몰비와 동등유사할 수 있다.

[0055] In one embodiment, the precursor further comprises cesium (Cs), (Co 1-x Fe x Cs z )Mo1O4(0 <x<1, 0.01≤z≤0.1)로 표시되는 것일 수 있다. 이때, z / x는 0.1 내지 1.1, 0.1 내지 1.0, 0.2 내지 0.95 또는 0.3 내지 0.9일 수 있다. 상기 만족하는 전구체로 촉매를 제조한 경우, 우수한 암모니아 합성 속도 향상의 효과를 구현할 수 있다. 또한 후술하는 전구체의 제조방법에 있어서, 상기 1-x는 투입하는 코발트 전구체의 몰비, x는 투입하는 철 전구체의 몰비, z는 투입하는 세슘 전구체의 몰비와 동등유사할 수 있다.

[0056] The present disclosure can provide an ammonia synthesis catalyst prepared from the precursor for preparing the ammonia synthesis catalyst described above. The ammonia synthesis catalyst can be prepared as a nitride-based catalyst by calcining the oxide precursor described above. The calcination method can utilize any conventional technology or known method without limitation.

[0057] In one embodiment, the catalyst is a nitride-based quaternary catalyst containing molybdenum (Mo), cobalt (Co), and iron (Fe), (Co 1-x Fe x )Mo1N y(0 <x<1, 0.2<y<0.4)로 표시될 수 있다. 이때 x는 상술한 전구체와 동일하므로 생략한다.

[0058] In one embodiment, the catalyst is a nitride-based four-component catalyst containing molybdenum (Mo), cobalt (Co), iron (Fe), and cesium (Cs), (Co 1-x Fe x Cs z )Mo1N y (0 <x<1, 0.2<y<0.4, 0.01≤z≤0.1)로 표시될 수 있다. 이때 x 및 y는 상술한 세슘 함유 전구체와 동일하므로 생략한다.

[0059] In one embodiment, the X-ray diffraction (XRD) analysis result of the ammonia synthesis catalyst may show a first peak at 2θ=32.5±0.2°, a second peak at 2θ=35.5±0.2°, a third peak at 2θ=40.0±0.2°, a fourth peak at 2θ=42.5±0.2°, and a fifth peak at 2θ=47.0±0.2°. In addition, each peak represents the crystal of the catalyst, as shown in Fig. 3, the first peak at 2θ = 32.5 ± 0.2° represents (004), the second peak at 2θ = 35.5 ± 0.2° represents (133), the third peak at 2θ = 40.0 ± 0.2° represents (224), the fourth peak at 2θ = 42.5 ± 0.2° represents (115), and the fifth peak at 2θ = 47.0 ± 0.2° represents (044). In addition, when the catalyst is not formed into the desired structure, for example, Fe is Co1Mo1N 0.33 In cases where it does not co-precipitate and floats on the surface, a peak indicating (110) may be seen at 2θ=44.5±0.2°, and this may not be preferred.

[0060] In one embodiment, the catalyst may be a pellet having an average particle size of 0.1 mm to 10 mm, 0.15 mm to 8 mm, 0.2 mm to 5 mm, 0.3 mm to 2 mm, or 0.5 mm to 1.5 mm, and may have a porous structure including a plurality of pores.

[0061] An ammonia synthesis catalyst having the above particle size range and containing multiple pores can significantly enhance the reaction activity of the catalyst by increasing the surface area exposed to contact with the reactants. In particular, since the ammonia synthesis catalyst predominantly contains pores having a pore size of 10 nm or greater, the catalyst specific surface area can significantly increase and the ammonia synthesis rate can be promoted.

[0062] In one embodiment, the volume occupied by pores having a pore size of 10 nm or more among the total pore volume of the catalyst may be 90% or more, 93% or more, 95% or more, or 97% or more. In the above range, the specific surface area is 7 m 2 / g or more, 7.2 m 2 / g or more or 7.5 m 2 / g or more, and advantageously, the specific surface area is 8 m 2 / g or more, 9 m 2 / g or more or 10 m 2 / g can be greater than or equal to, but not limited to, 100 m 2 / g or less, 95 m 2 / g or less or 90 m 2 / g can be less.

[0063] Hereinafter, the precursor for manufacturing the above-described ammonia synthesis catalyst and the method for manufacturing the ammonia synthesis catalyst using the same will be described in detail.

[0064] The present disclosure provides a method for producing an ammonia synthesis catalyst, comprising: a step of producing a precursor for producing an ammonia synthesis catalyst in a pellet shape; and an ammonolysis step of heat-treating the precursor for producing an ammonia synthesis catalyst in an ammonia atmosphere to produce an ammonia synthesis catalyst. Descriptions of the precursor for producing an ammonia synthesis catalyst and the ammonia synthesis catalyst are the same as those described above, and are therefore omitted.

[0065] According to one embodiment of the present disclosure, the step of manufacturing a precursor for manufacturing an ammonia synthesis catalyst in the shape of a pellet may include the steps of sequentially introducing a metal precursor and drying, calcining, and molding.

[0066] In one embodiment, the precursor preparation step may include: (S10) introducing a molybdenum precursor and a cobalt precursor; (S20) introducing an organic acid of C3-10; (S30) preparing a precursor solution by introducing an iron precursor; (S40) heating the precursor solution to prepare a precursor powder for preparing an ammonia synthesis catalyst; and (S50) molding the precursor powder.

[0067] In the above step (S10), the molybdenum precursor and the cobalt precursor can be sequentially added to the solvent, and at this time, it is preferable to add and dissolve the cobalt precursor after the molybdenum precursor is completely dissolved.

[0068] The above molybdenum precursors include, but are not limited to, Na2MoO4·H2O, (NH4)2MoO4·4H2O and (NH4)6Mo7O. 24 ·It may be at least one selected from the group consisting of 4H2O, etc.

[0069] As non-limiting examples, the cobalt precursors include CoCl2, CoCl2·6H2O, CoCl2·xH2O, [Co(NH3)6]Cl -, Co(NO3)2·6H2O, and Co(CH3COO)2·4H2O.

[0070] In one embodiment, 50 to 100 moles, 70 to 99 moles, or 90 to 98 moles of the cobalt precursor may be added per 100 moles of the molybdenum precursor.

[0071] It is preferable that the step of adding the organic acid (S20) above be performed after the cobalt precursor is completely dissolved, and in particular, if the organic acid is added after the iron precursor is added as in the past, the physical properties targeted by the present invention cannot be achieved, which is not preferable.

[0072] The organic acid may be a C3-10 organic acid or chelating agent, or a C5-7 organic acid or chelating agent, and may be at least one selected from the group consisting of, but not limited to, adipic acid, citric acid, glutaric acid, tartaric acid, malic acid, fumaric acid, adipic acid, succinic acid, sucrose, oxalic acid, ethylenediaminetetraacetic acid (EDTA), hydroxyethanediphosphonic acid (HEDP), and the like.

[0073] For 100 moles of the sum of the molybdenum precursor, cobalt precursor, and iron precursor, the organic acid may be added in an amount of 50 to 200 moles, 70 to 180 moles, or 90 to 150 moles.

[0074] In the step of introducing the iron precursor (S30), it is preferable to introduce the iron precursor and stir and dissolve it after completely dissolving the organic acid, which is the previous step.

[0075] The above iron precursor may be, for non-limiting examples, at least one selected from the group consisting of FeCl3, FeCl2, Fe(NO3)3·9H2O, FeCl3·6H2O, and FeCl2·4H2O.

[0076] In one embodiment, the iron precursor may be added in an amount of 0.5 to 80 moles, 1 to 75 moles, or 5 to 70 moles per 100 moles of the molybdenum precursor.

[0077] In the above steps (S10) to (S30), the solvent may include distilled water, and the dissolution temperature may be room temperature, 10 to 50°C, or 20 to 40°C. In addition, the stirring speed (rpm) is not significantly limited as long as the mixture in the container does not overflow and the entire mixture can be properly mixed.

[0078] In one embodiment, the step (S30) may be performed by a conventional or known co-precipitation method. A precursor for preparing an ammonia synthesis catalyst may be prepared by using a co-precipitation method in which a solution in which a cobalt precursor, a molybdenum precursor, a citric acid, and an iron precursor are sequentially added by performing step (S30) is heated to a temperature of 60°C or higher, 60 to 180°C, or 100 to 160°C to evaporate the solvent while inducing precipitation of the above-described metal salts.

[0079] According to another embodiment of the present disclosure, the method may further include a step of adding a polyhydric alcohol to the precursor solution after step (S30) and before step (S40). It is preferable to add the polyhydric alcohol and stir and dissolve it after the iron precursor is completely dissolved in the solvent in step (S30).

[0080] In particular, when the polyhydric alcohol is heated together with the organic acid described above, as illustrated in FIG. 2, the organic acid is organically linked through an esterification reaction, and the polyhydric alcohol is bonded between the organic acid linked to metal ions such as molybdenum, cobalt, and iron, thereby acting as a binder, thereby further improving the bonding strength and durability of the precursor structure in the calcination step described below. The organic acid and the polyhydric alcohol can be polymerized through an esterification reaction, and the precursor including the polymer can have significantly improved structural stability compared to the prior art. If the polyhydric alcohol is not included, the durability of the precursor in the calcination step is insufficient, making it difficult to achieve the properties desired in the present invention, and thus may not be preferred. A catalyst manufactured using the same can achieve a remarkable effect of improving the ammonia synthesis rate.

[0081] The above polyhydric alcohols can be used without limitation as long as they have two or more or three or more hydroxyl groups, and preferably, polyhydric alcohols having two or three hydroxyl groups can be used. Non-limiting examples thereof include at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, 1,4-butynediol, 1,5-pentanediol, neopentylglycol, bis(hydroxymethyl)cyclohexane, 2-methyl-1,3-propanediol, methylpentanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, polytetrahydrofuran, polycarbonate diol, and polycaprolactone diol.

[0082] In one embodiment, the molar ratio of the polyhydric alcohol to the organic acid may be 0.05 to 5.0, 0.1 to 2.0, 0.3 to 1.5, or 0.8 to 1.3, or the molar ratio may be 0.05 to 5.0, 0.1 to 2.0, 0.3 to 1.5, or 0.8 to 1.3. Alternatively, the polyhydric alcohol may be added in an amount of 1 to 100 parts by weight, 5 to 70 parts by weight, or 15 to 50 parts by weight, based on 100 parts by weight of the organic acid. In the case of a precursor manufactured by satisfying the above range, an ammonia synthesis catalyst having an excellent ammonia synthesis rate can be manufactured.

[0083] The above polyhydric alcohol introduction step may be a method of manufacturing a precursor for preparing an ammonia synthesis catalyst by using a coprecipitation method in which a solution in which a cobalt precursor, a molybdenum precursor, a citric acid, an iron precursor, and a polyhydric alcohol are sequentially introduced is heated to a temperature of 60°C or higher, 60°C to 180°C, or 100°C to 160°C to evaporate the solvent while inducing precipitation of the above-described metal salts.

[0084] According to another embodiment of the present disclosure, the polyhydric alcohol introduction step may be performed by a coprecipitation method described in a conventional or known method. Specifically, a precursor for preparing an ammonia synthesis catalyst may be prepared by using a coprecipitation method in which a solution in which a cobalt precursor, a molybdenum precursor, citric acid, an iron precursor, a cesium precursor, and a polyhydric alcohol are all sequentially introduced is heated to a temperature of 60°C or higher, 60°C to 180°C, or 100°C to 160°C to evaporate the solvent while inducing precipitation of the above-described metal salts.

[0085] In another embodiment of the present disclosure, a step of introducing a cesium (Cs) precursor may be further included after step (S30) and before step (S40). It is preferable that the step of introducing the cesium (Cs) precursor be performed by introducing the cesium precursor and stirring and dissolving it after the iron precursor in the previous step has been completely dissolved in the solvent.

[0086] The above cesium precursor may be, for non-limiting examples, at least one selected from the group consisting of CsCl, CsNO3, and CH3COOCs.

[0087] In one embodiment, the cesium precursor may be introduced in an amount of 0.5 to 30 moles, 1 to 15 moles, or 5 to 10 moles per 100 moles of the molybdenum precursor. Alternatively, the cesium precursor may be introduced in an amount of 10 to 110 moles, 20 to 80 moles, or 30 to 60 moles per 100 moles of the iron precursor.

[0088] According to another embodiment of the present disclosure, the step of introducing the cesium (Cs) precursor may be performed by a co-precipitation method described in a conventional or known method. The precursor for preparing an ammonia synthesis catalyst may be prepared by using a co-precipitation method in which a solution in which a cobalt precursor, a molybdenum precursor, a citric acid, an iron precursor, and a cesium precursor are sequentially introduced is heated to a temperature of 60° C. or higher, 60 to 180° C., or 100 to 160° C. to evaporate the solvent while inducing precipitation of the above-described metal salts, up to the step of introducing the cesium (Cs) precursor.

[0089] In addition, when adding a cesium (Cs) precursor and a polyhydric alcohol to the precursor solution, it is preferable to add the cesium precursor after the iron precursor has completely dissolved in the solvent, stir and dissolve it, and then add the polyhydric alcohol after the cesium precursor has completely dissolved, stir and dissolve it.

[0090] According to one embodiment of the present disclosure, the step (S40) may be to induce precipitation of metal salts using a co-precipitation method, and then dry and calcinate the precipitate to prepare a precursor powder for preparing an ammonia synthesis catalyst. The drying may be performed in a drying oven at a temperature of 100°C or higher, 110 to 200°C, until completely dried, for 1 hour or more, preferably 3 hours or more, but is not limited thereto. In addition, the calcination step may be to calcinate at a temperature of 400°C to 800°C, 450°C to 750°C, or 500°C to 750°C for 1 hour or more, 2 to 4 hours. When calcined in the above temperature range, the catalytic activity is improved, and in a more advantageous example, when calcined at a low temperature in a temperature range of 400°C to 600°C or 500°C to 600°C, the I of the catalyst precursor prepared 26.5˚ / I 28.5˚ The value can be increased to further improve the catalytic activity.

[0091] After the above step (S40), (S50) the precursor powder for manufacturing an ammonia synthesis catalyst may be molded to finally manufacture an ammonia synthesis catalyst precursor. The molding may be performed by compressing and molding the precursor powder for manufacturing an ammonia synthesis catalyst into pellets.

[0092] The ammonia synthesis catalyst may be manufactured by performing a step of performing an ammonolysis reaction on the precursor for an ammonia synthesis catalyst manufactured by the above method in an ammonia atmosphere at a temperature of 400°C to 800°C, 500°C to 750°C, 600°C to 700°C, or 650°C to 700°C for 10 minutes or more and 30 minutes to 2 hours. The ammonolysis reaction may utilize commonly used or known conditions without limitation.

[0093] An ammonia synthesis catalyst can be manufactured by converting an oxide precursor into a nitride through an ammonium decomposition reaction. Furthermore, the catalyst's specific surface area can be enhanced by creating numerous pores on the surface of the pellet-shaped precursor particles.

[0094] Hereinafter, a method for synthesizing ammonia using an ammonia synthesis catalyst according to one embodiment of the present disclosure will be described in more detail.

[0095] The present disclosure can provide an ammonia synthesis method using the ammonia synthesis catalyst described above. When synthesizing ammonia using the ammonia synthesis catalyst described above, the ammonia synthesis rate is significantly improved compared to the amount of catalyst used, thereby achieving the effect of high ammonia synthesis efficiency at low temperature and low pressure.

[0096] The above ammonia synthesis catalyst may further include a conventional or known support. The support may be any material capable of supporting or supporting an active metal, and may include, for example, one or more selected from cerium oxide, titanium oxide, vanadium oxide, zirconium oxide, zinc oxide, lanthanum oxide, magnesium oxide, silicon oxide, aluminum oxide, zeolite, and activated carbon.

[0097] According to one embodiment of the present disclosure, the ammonia synthesis catalyst may further include a cocatalyst, and the cocatalyst may include one or more of an alkali metal and an alkaline earth metal (barium, cesium, rubidium, strontium, potassium, calcium, sodium, etc.).

[0098] The above ammonia synthesis method can be performed at lower temperature and pressure than conventional techniques, and specifically, can be performed under temperature conditions of 500°C or less, 250°C to 500°C, 250°C to 450°C, or 300°C to 410°C, and pressure conditions of 50 bar or less, 1 bar to 30 bar, 1 bar to 20 bar, or 2 bar to 11 bar.

[0099] According to one embodiment of the present disclosure, the ammonia synthesis catalyst formed into a pellet shape can significantly improve the ammonia synthesis rate under low temperature and low pressure conditions. More specifically, the ammonia synthesis rate is 11.5 mmol / g. cat ·h or more, 15 mmol / g cat ·h or more, 17 mmol / g cat ·h or more, 18 mmol / g cat ·h or more, 19 mmol / g cat ·h or more or 20 mmol / g cat ·h may be greater than or equal to 25 mmol / g, preferably cat ·h can be more than 100 mol / g. The upper limit is not limited, but cat ·h may be less.

[0100] Hereinafter, the present disclosure will be described in more detail through examples.

[0101] (Manufacturing Example 1)

[0102] Ammonium molybdate hydrate ((NH4)6Mo7O) as a precursor in 250 mL of distilled water 24·4H2O) 3.7 g (3.0 mmol), cobalt nitrate hydrate (Co(NO3)2·6H2O) 4.7 g (16 mmol), citric acid 7.3 g (30 mmol), and iron nitrate hydrate (Fe(NO3)3·9H2O) 0.53 g (1.3 mmol) were sequentially added and stirred, and then ethylene glycol 2.0 mL (30 mmol) was added last. At this time, the molar ratio of ethylene glycol to the added citric acid satisfied 1.0.

[0103] Afterwards, the mixture was heated in a temperature range of 60 to 90°C to evaporate the distilled water and stirred until the mixture began to swell in a sponge shape. When the mixture began to swell, the beaker was transferred to an oven and dried at 150°C for more than 6 hours. After drying was completed, the sponge-shaped dried product was pulverized. The pulverized dried product was heated at 5°C per minute to 700°C in an air atmosphere and then calcined for 3 hours to produce a precursor powder for preparing an ammonia synthesis catalyst [(Co 1-x Fe x )Mo1O4(x=0.075)] was obtained.

[0104] (Manufacturing Example 2)

[0105] The same procedure as in Manufacturing Example 1 was followed, except that iron nitrate hydrate was not added.

[0106] (Manufacturing Example 3)

[0107] The same procedure as in Manufacturing Example 1 was followed, except that the order of citric acid and iron nitrate hydrate was changed.

[0108] (Manufacturing Example 4)

[0109] The same procedure as Manufacturing Example 1 was followed, except that citric acid was added first.

[0110] (Manufacturing Example 5)

[0111] The same procedure as in Manufacturing Example 4 was followed, except that ammonium molybdate hydrate was added after iron nitrate hydrate was added.

[0112] (Manufacturing Example 6)

[0113] The same procedure as Manufacturing Example 1 was followed, except that iron nitrate hydrate was introduced first.

[0114] (Manufacturing Example 7)

[0115] The same procedure as in Manufacturing Example 6 was followed, except that the order of citric acid and cobalt nitrate hydrate was changed.

[0116] (Manufacturing Example 8)

[0117] A precursor powder for preparing an ammonia synthesis catalyst [(Co] was prepared in the same manner as in Manufacturing Example 1, except that 0.35 g of iron nitrate hydrate and 4.83 g of cobalt nitrate hydrate were added. 1-x Fe x )Mo1O4(x=0.05)] was obtained.

[0118] (Manufacturing Example 9)

[0119] A precursor powder for preparing an ammonia synthesis catalyst [(Co] was prepared in the same manner as in Manufacturing Example 1, except that 0.71 g of iron nitrate hydrate and 4.58 g of cobalt nitrate hydrate were added. 1-x Fe x )Mo1O4(x=0.1)] was obtained.

[0120] (Manufacturing Example 10)

[0121] A precursor powder for preparing an ammonia synthesis catalyst [(Co] was prepared in the same manner as in Manufacturing Example 1, except that 0.88 g of iron nitrate hydrate and 4.45 g of cobalt nitrate hydrate were added. 1-x Fe x )Mo1O4(x=0.125)] was obtained.

[0122] (Manufacturing Example 11)

[0123] Ammonium molybdate hydrate ((NH4)6Mo7O) as a precursor in 250 mL of distilled water 24 4H2O) 3.69 g (3.0 mmol), cobalt nitrate hydrate (Co(NO3)26H2O) 4.45 g (15 mmol), citric acid 7.3 g (30 mmol), and iron nitrate hydrate (Fe(NO3)3·9H2O) 0.88 g (2 mmol) were sequentially added and stirred, then cesium nitrate (CsNO3) 0.33 g (1.7 mmol) was added and stirred, and then ethylene glycol 2.0 mL (30 mmol) was added and stirred, and the same procedure as in Manufacturing Example 1 was performed according to the co-precipitation method, except that precursor powder for preparing an ammonia synthesis catalyst [(Co 1-x Fe x Cs z )Mo1O4(x=0.125, z=0.1)] was obtained.

[0124] (Manufacturing Example 12)

[0125] The same procedure as in Manufacturing Example 1 was followed, except that ethylene glycol was not added.

[0126] (Manufacturing Example 13)

[0127] The same procedure as in Manufacturing Example 1 was followed, except that 1.0 mL (15 mmol) of ethylene glycol was added. At this time, the molar ratio of ethylene glycol to citric acid added satisfied 0.5.

[0128] (Manufacturing Example 14)

[0129] The same procedure as in Manufacturing Example 1 was followed, except that 4 mL (60 mmol) of ethylene glycol was added. At this time, the molar ratio of ethylene glycol to citric acid added satisfied 2.0.

[0130] (Manufacturing Example 15)

[0131] The same procedure as in Manufacturing Example 11 was followed, except that the pulverized dried product was calcined at 550°C in an air atmosphere.

[0132] (Example 1)

[0133] Preparation of precursors for ammonia synthesis catalysts

[0134] The precursor powder for manufacturing an ammonia synthesis catalyst manufactured in the above Manufacturing Example 1 was put into a pelletizer and compressed and molded to manufacture a precursor for manufacturing an ammonia synthesis catalyst having a particle size of 200 μm.

[0135] Ammonia synthesis catalyst manufacturing

[0136] The precursor for manufacturing the above ammonia synthesis catalyst was put into a kiln, and the temperature was raised at 10°C per minute to 675°C in an ammonia atmosphere with a molar ratio of H2 / N2 of 3, and then maintained for 2 hours to produce an ammonia synthesis catalyst [(Co 1-x Fe x )Mo1N 0.33 (x=0.075)] was manufactured.

[0137] (Example 2)

[0138] An ammonia synthesis catalyst [(Co] was prepared in the same manner as in Example 1, except that the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 8 was used. 1-x Fe x )Mo1N 0.33 (x=0.05)] was manufactured.

[0139] (Example 3)

[0140] Except for using the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 9, the same method as Example 1 was performed, and finally an ammonia synthesis catalyst [(Co 1-x Fe x )Mo1N 0.33 (x=0.1)] was manufactured.

[0141] (Example 4)

[0142] Except for using the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 10, the same method as Example 1 was performed, and finally an ammonia synthesis catalyst [(Co 1-x Fe x )Mo1N 0.33 (x=0.125)] was manufactured.

[0143] (Example 5)

[0144] Except for using the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 11, the same method as Example 1 was performed, and finally an ammonia synthesis catalyst [(Co 1-x Fe x Cs z )Mo1N 0.33 (x=0.125, z=0.1)] was manufactured.

[0145] (Example 6)

[0146] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 12 was used.

[0147] (Example 7)

[0148] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 13 was used.

[0149] (Example 8)

[0150] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 14 was used.

[0151] (Example 9)

[0152] The same method as Example 1 was used, except that the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 15 was used.

[0153] (Example 10)

[0154] The same method as Example 1 was performed, except that the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 15 was pelletized to prepare an ammonia synthesis catalyst precursor having a particle size of 500 μm.

[0155] (Example 11)

[0156] An ammonia synthesis catalyst was prepared in the same manner as in Example 10, except that an ammonia synthesis catalyst precursor having a particle size of 1000 μm was prepared.

[0157] (Example 12)

[0158] An ammonia synthesis catalyst was prepared in the same manner as in Example 10, except that an ammonia synthesis catalyst precursor having a particle size of 2000 μm was prepared.

[0159] (Comparative Example 1)

[0160] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 2 was used.

[0161] (Comparative Example 2)

[0162] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 3 was used.

[0163] (Comparative Example 3)

[0164] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 4 was used.

[0165] (Comparative Example 4)

[0166] The same method as Example 1 was used, except that the precursor powder for preparing an ammonia synthesis catalyst of Manufacturing Example 5 was used.

[0167] (Comparative Example 5)

[0168] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 6 was used.

[0169] (Comparative Example 6)

[0170] The same method as Example 1 was used, except that the precursor powder for the ammonia synthesis catalyst of Manufacturing Example 7 was used.

[0171] (Comparative Example 7)

[0172] The precursor powder for manufacturing an ammonia synthesis catalyst of Manufacturing Example 15 was introduced into a kiln, and the temperature was raised at 10°C per minute to 675°C in an ammonia atmosphere with a molar ratio of H2 / N2 of 3, and then maintained for 2 hours to manufacture an ammonia synthesis catalyst.

[0173] (Comparative Example 8)

[0174] The precursor powder for manufacturing an ammonia synthesis catalyst of Manufacturing Example 15 was introduced into a kiln, and the temperature was increased at 10°C per minute to 675°C in an ammonia atmosphere with a molar ratio of H2 / N2 of 3, and then maintained for 2 hours. Then, it was introduced into a pelletizer, compressed, and molded to manufacture an ammonia synthesis catalyst having a particle size of 1000 μm.

[0175] (Comparative Example 9)

[0176] The same method as Comparative Example 7 was performed, except that the precursor powder for manufacturing an ammonia synthesis catalyst of Manufacturing Example 1 was used.

[0177] (Evaluation Example 1) X-ray diffraction analysis evaluation

[0178] X-ray diffraction analysis of precursor powders for the preparation of an ammonia synthesis catalyst and an ammonia synthesis catalyst was performed. Specifically, X-ray diffraction (XRD) analysis was performed using an EMPYREAN from PANalytical as an XRD analyzer (X-ray Diffractometer) under the following conditions.

[0179] - Light source (X-ray source): Cu-Kα radiation

[0180] - Power: 40 KV x 30mA

[0181] - Mode: Continuous scan mode

[0182] - Scan angle range: 10°~50°

[0183] - Scan speed: 5° / min

[0184] The X-ray diffraction analysis spectrum is shown in Fig. 1 and Fig. 3 below, and the peak intensity (I) at 2θ = 28.5 ± 0.2° 28.5°) and peak intensity (I) at 2θ=26.5±0.2° 26.5° ) of the rain (I 26.5° / I 28.5° ) was calculated and shown in Table 1 below. In addition, in Table 1 below, Mo represents ammonium molybdate hydrate, Co represents cobalt nitrate hydrate, Fe represents iron nitrate hydrate, Cs represents cesium nitrate, CA represents citric acid, and EG represents ethylene glycol.

[0185] Precursor introduction sequence I 26.5° / I 28.5° Manufacturing Example 1Mo → Co → CA → Fe → EG0.66 Manufacturing Example 3Mo → Co → Fe → CA → EG0.21 Manufacturing Example 4CA → Mo → Co → Fe → EG0.19 Manufacturing Example 5CA → Co → Fe → Mo → EG0.23 Manufacturing Example 6Fe → Mo → Co → CA → EG0.27 Manufacturing Example 7Fe → Mo → CA → Co → EG0.32 Manufacturing Example 11Mo → Co → CA → Fe → Cs → EG (700℃ firing)3.36 Manufacturing Example 15Mo → Co → CA → Fe → Cs → EG (500℃ firing)5.67

[0186] As shown in Table 1 above, when the precursor is manufactured in the same order as Manufacturing Example 1, I 26.5° / I 28.5°The precursors for preparing an ammonia synthesis catalyst of Manufacturing Examples 2 to 7, which had a different precursor preparation order from Manufacturing Example 1, satisfied a value of 0.4 or more, preferably 0.6 or more, but 26.5° / I 28.5° It was confirmed that a precursor for manufacturing an ammonia synthesis catalyst having a structure different from that of Manufacturing Example 1 was manufactured, as the value was less than 0.4, more specifically, less than 0.35. Specifically, when manufacturing a precursor using the methods of Manufacturing Examples 2 to 7, it was not synthesized according to the ratio in which the metal precursor was introduced, but a structure (Co) composed of a specific ratio 0.7 Fe 0.3 The formation of Mo1O4) is desirable to minimize because it has the problem of low ammonia synthesis efficiency. Therefore, in one embodiment, by adopting an injection order that can solve this problem, it is possible to manufacture a precursor having a structure in which Fe is introduced while maintaining the CoMoO4 structure while suppressing the formation of a specific structure that causes low efficiency.

[0187] Referring to Figures 1 and 3, Co 0.7 Fe 0.3 I which stands for Mo1O4 28.5° The lower the peak intensity, the more I indicates CoMoO4. 26.5° The higher the peak intensity, the more desirable it is, i.e., I 26.5° / I 28.5° A precursor having a value of 0.4 or more, preferably 0.6 or more, is highly desirable for producing a catalyst having a high ammonia synthesis rate. For all comparative examples except Manufacturing Example 1, Manufacturing Example 11, and Manufacturing Example 15, I 26.5° / I 28.5° As the value is shown to be low, less than 0.4, it can be seen that a catalyst having an excellent ammonia synthesis rate can be manufactured by adopting the injection order according to Manufacturing Example 1. In the case of Manufacturing Examples 11 and 15, which are precursors for manufacturing a four-component ammonia synthesis catalysts containing more Cs while maintaining the injection order according to Manufacturing Example 1, I 26.5° / I 28.5° The values ​​were very high at 3.36 and 5.67, respectively, confirming that the ammonia synthesis rate could be significantly improved.

[0188] In addition, an ammonia synthesis catalyst manufactured using the precursor powder for manufacturing the above ammonia synthesis catalyst was subjected to X-ray diffraction analysis, and the result is shown in Fig. 4. Referring to Fig. 4, in the precursor powder of Manufacturing Example 15, a peak originating from CoMoO4 of the β-phase was strongly detected at θ=26.5±0.2°, indicating that the CoMoO4 structure was effectively maintained.

[0189] The ammonia synthesis catalysts of Examples 10, 11 and Comparative Example 7 manufactured using the precursor powder of Manufacturing Example 15 detected a first peak at 2θ=32.5±0.2°, a second peak at 2θ=35.5±0.2°, a third peak at 2θ=40.0±0.2°, a fourth peak at 2θ=42.5±0.2° and a fifth peak at 2θ=47.0±0.2°. Each peak represents a crystal of the catalyst, the first peak at 2θ = 32.5 ± 0.2° represents a crystal of the (004) plane, the second peak at 2θ = 35.5 ± 0.2° represents a crystal of the (133) plane, the third peak at 2θ = 40.0 ± 0.2° represents a crystal of the (224) plane, the fourth peak at 2θ = 42.5 ± 0.2° represents a crystal of the (115) plane, and the fifth peak at 2θ = 47.0 ± 0.2° represents a crystal of the (044) plane.

[0190] Fe is Co1Mo1N 0.33 When Fe and Cs are not co-precipitated and are floating on the surface, a peak for the (110) plane can be observed at 2θ=44.5±0.2°. However, the ammonia synthesis catalysts of Examples 10 and 11 do not have a peak observed at 2θ=44.5±0.2°, indicating that Fe and Cs are Co1Mo1N 0.33 It was confirmed that an ammonia synthesis catalyst capable of effectively co-precipitating and improving the ammonia synthesis rate was prepared.

[0191] In addition, in order to calculate the crystal size of the ammonia synthesis catalyst from the XRD spectrum, the crystal size of the ammonia synthesis catalysts of Comparative Example 7 and Examples 9 to 11 was calculated using the Scherrer equation. As a result, the ammonia synthesis catalyst of Comparative Example 7 had a crystal size of 33.1 nm, and the ammonia synthesis catalysts of Examples 9 to 11 showed crystal sizes of 33.5 nm, 35.5 nm, and 37.0 nm, respectively. Therefore, it was confirmed that as the size of the catalyst pellet increased, the crystal size increased, thereby improving the ammonia synthesis efficiency.

[0192] (Evaluation Example 2) Catalyst composition evaluation

[0193] X-ray fluorescence analysis (XRF) of the ammonia synthesis catalyst was performed. Specifically, X-ray fluorescence analysis was performed using a D / Max IIIB from Rigaku, and the measurement results are shown in Table 2 below.

[0194] Precursor powder type Catalyst particle size Cs / Mo molar ratio Fe / Mo molar ratio Co / Mo molar ratio Manufacturing example 1 - Powder (<100 ㎛) - 0.075 0.925 Manufacturing example 15 - Powder (<100 ㎛) 0.10 125 0.975 Example 1 Manufacturing example 1 200 ㎛ - 0.075 0.925 Example 9 Manufacturing example 15 200 ㎛ 0.10 125 0.975 Example 10 Manufacturing example 15 500 ㎛ 0.10 125 0.975 Example 11 Manufacturing example 15 1000 ㎛ 0.10 125 0.975 Example 12 Manufacturing example 15 2000 ㎛ 0.10 125 0.975

[0195] Referring to Table 2, when producing precursor powders using the methods of Manufacturing Examples 1 and 15, as Fe was introduced while maintaining CoMoO4, precursor powders were formed according to the ratio in which each metal component was introduced, and the metal ratio could be maintained during the subsequent precursor production and catalyst production processes. In particular, as in Examples 9 to 12, it was confirmed that the metal components maintained a constant composition even when the size of the catalyst particles changed, thereby producing an ammonia synthesis catalyst with excellent activity.

[0196] (Evaluation Example 3) Catalyst Structure Evaluation

[0197] To analyze the pore structure of the ammonia synthesis catalyst, nitrogen adsorption-desorption analysis was performed using a TriStar 3000 (Micromeritics). The specific surface area and total pore volume (P / P0 = 0.99) were calculated using the BET method, the mesopore and macropore size distributions were calculated using the BJH curve, and the micropore volume was calculated using the t-plot method. The results of the catalyst structure analysis are shown in Fig. 5 and Table 3.

[0198] Particle size (㎛) BET surface area (m 2 / g)Total pore volume (cm) 3 / g)Pore volume (cm) with a diameter of 10 nm or more 3 / g) Manufacturing Example 15<1003.460.0110 Example 92007.580.0330.032 Example 105009.650.0390.038 Example 1110009.770.0480.047 Example 12200011.140.0560.055 Comparative Example 810005.150.0210.021

[0199] As shown in Table 3 and Fig. 5, the catalyst precursor powder of Manufacturing Example 15 has a specific surface area of ​​3.46 m 2 / g, and the total pore volume is 0.011 cm 3 / g was low, and there were no pores with a diameter greater than 10 nm.

[0200] On the other hand, the ammonia synthesis catalyst manufactured by forming the precursor powder of Manufacturing Example 15 into a pellet shape as in Examples 9 to 12 and then nitriding it has a specific surface area of ​​7.5 m 2 / g or more and total pore volume of 0.033 cm 3 / g or more, and it was confirmed that the volume of medium- to large-sized pores with a diameter of 10 nm or more among the pores increased significantly.

[0201] Specifically, the pores with a diameter of 10 nm or more accounted for more than 96.9% of the total pore volume, and most of the pores. Among them, Example 12, in which the catalyst particle size was 2000 ㎛, had a specific surface area of ​​11.14 m 2 / g was the largest, and the ratio of the volume of pores with a diameter of 10 nm or more among the total pore volume was 98.2%, confirming that the volume of small pores with a diameter of less than 10 nm was reduced and large pores with a diameter of 10 nm or more were effectively developed.

[0202] In the case of Comparative Example 8, in which the precursor powder of Manufacturing Example 15 was nitrided and then molded into a pellet shape, the pores formed during the nitriding process shrank through the molding process, resulting in a decrease in the specific surface area, and thus a significantly lower specific surface area and total pore volume compared to Example 11, which had the same catalyst particle size.

[0203] (Evaluation Example 4) Evaluation of ammonia synthesis efficiency

[0204] A fixed-bed reactor was charged with 0.05 g of an ammonia synthesis catalyst and 0.2 g of SiC as an inert material. To activate the catalyst surface, the temperature was increased from atmospheric pressure to 700°C at a rate of 5°C per minute while nitrogen and hydrogen were injected at a flow rate of 15 mL / min and 45 mL / min, respectively, and maintained for 1 hour. After cooling to 400°C while maintaining the flow rates of nitrogen and hydrogen, the reactor was pressurized to 10 bar and the space velocity was 72,000 ml / g. cat Ammonia was synthesized in h for 2 hours. The amount of synthesized ammonia was confirmed by neutralizing it in a 0.3 mM sulfuric acid solution, and the degree of neutralization of the sulfuric acid solution was confirmed by measuring the conductivity value of a pH meter in real time.

[0205] Referring to non-patent literature SE Sivan et al., J. Catal. 408 (2022) 316-328, the mole fraction (MF) and synthesis rate of the produced ammonia were calculated according to Equations 1 and 2 below and are shown in Tables 4 to 7 below. In Equation 1 below, M NH3 is the number of moles of synthesized ammonia, and M N2 is the number of moles of unreacted nitrogen, and M H2 is the number of moles of unreacted hydrogen.

[0206] [Formula 1]

[0207] Ammonia mole fraction (MF)(%)={M NH3 / (M NH3 +M N2 +M H2 )} Х 100

[0208] [Formula 2]

[0209] Ammonia synthesis rate (mmol / g) cat ·h)={Ammonia mole fraction (MF) Х60 / {(1+MF)Хcatalyst mass (g) cat )Х22.08}}Х100

[0210] Precursor powder type, manufacturing sequence, catalyst particle size, ammonia synthesis rate (mmol / g) cat.h) Example 1 Manufacturing Example 1 Nitriding treatment after molding 200 ㎛ 11.8 Example 5 Manufacturing Example 11 Nitriding treatment after molding 200 ㎛ 16.6 Example 9 Manufacturing Example 15 Nitriding treatment after molding 200 ㎛ 21.3 Example 10 Manufacturing Example 15 Nitriding treatment after molding 500 ㎛ 25.8 Example 11 Manufacturing Example 15 Nitriding treatment after molding 1000 ㎛ 27.5 Example 12 Manufacturing Example 15 Nitriding treatment after molding 2000 ㎛ 30.1 Comparative Example 7 Manufacturing Example 15 Molding X < 100 ㎛ 21.1 Comparative Example 8 Manufacturing Example 15 Molding after nitriding 1000 ㎛ 14.6 Comparative Example 9 Manufacturing Example 1 Molding X < 100 ㎛ 10.6

[0211] As shown in Table 4, by manufacturing a catalyst precursor formed into a pellet shape, the ammonia synthesis rate was significantly improved. In the ammonia synthesis catalyst manufactured using the precursor powder of Manufacturing Example 1 containing Co, Mo, and Fe, the ammonia synthesis catalyst of Comparative Example 9, which was manufactured by nitriding the precursor powder without forming it into a pellet shape, had an ammonia synthesis rate of 10.6 mmol / g. cat ·h was low, but the ammonia synthesis catalyst of Example 1, which was formed into a pellet shape from precursor powder and then nitrided, had an ammonia synthesis rate of 11.8 mmol / g. cat ·h improved catalytic performance.

[0212] Likewise, when the precursor powder of Manufacturing Example 15 containing Cs along with Co, Mo, and Fe was used, the powder catalyst of Comparative Example 7 had an ammonia synthesis rate of 21.1 mmol / g. cat ·h, but the ammonia synthesis catalysts of Examples 9 to 12 having a pellet shape had 21.3 mmol / g cat · It showed an ammonia synthesis rate that was improved to more than h. In particular, it was confirmed that the ammonia synthesis rate increased as the catalyst particle size increased. Example 10, in which the catalyst particle size was 500 ㎛, showed an ammonia synthesis rate of 25.8 mmol / g. cat·h, Example 11 with a catalyst particle size of 1000 ㎛ has an ammonia synthesis rate of 27.5 mmol / g cat · Example 12, with h and catalyst particle size of 2000 ㎛, has an ammonia synthesis rate of 30.1 mmol / g cat · It was measured as h. As the size of the catalyst particles increases, pores with a diameter of 10 nm or more develop, and as the specific surface area and pore volume increase, there are abundant active sites that promote the ammonia synthesis reaction, so the ammonia synthesis rate can be effectively increased even under low-temperature and low-pressure conditions.

[0213] In particular, in the case of the ammonia synthesis catalyst of Example 9, which was manufactured by molding the precursor powder of Manufacturing Example 15 manufactured by calcination at 550 ℃ and then nitriding, the ammonia synthesis rate was 21.3 mmol / g. cat · It was measured as h. This was a significantly higher ammonia synthesis rate than the catalyst of Example 5 manufactured using precursor powder calcined at 700°C, and could effectively improve the ammonia synthesis efficiency during low-temperature calcination.

[0214] On the other hand, the ammonia synthesis catalyst of Comparative Example 8 was manufactured in the form of a pellet by nitriding and then molding the precursor powder for manufacturing an ammonia synthesis catalyst as described above. As a result, the surface area and pore volume actually decreased as the pores created during the nitriding process shrank during the molding process. Accordingly, it showed a significantly low ammonia synthesis rate despite the catalyst particle size being 1000 μm.

[0215] Precursor powder type Catalyst shape Particle size (㎛) Ammonia synthesis rate (mmol / g) cat.h) Example 1 Manufacturing Example 1 Pellet 20011.8 Example 5 Manufacturing Example 11 Pellet 20016.6 Comparative Example 1 Manufacturing Example 2 Pellet 2006.1 Comparative Example 2 Manufacturing Example 3 Pellet 2006.4 Comparative Example 3 Manufacturing Example 4 Pellet 2006.2 Comparative Example 4 Manufacturing Example 5 Pellet 2006.6 Comparative Example 5 Manufacturing Example 6 Pellet 2007.1 Comparative Example 6 Manufacturing Example 7 Pellet 2007.4

[0216] As described above, the ammonia synthesis catalysts of Manufacturing Examples 2 to 7 have a structure (Co) composed of a specific ratio when producing precursor powder. 0.7 Fe 0.3 As Mo1O4) is formed, I 26.5° / I 28.5° The value was very low, less than 0.4. Accordingly, the ammonia synthesis catalysts of Comparative Examples 1 to 6, each manufactured using the precursor powders of Manufacturing Examples 2 to 7, had an ammonia synthesis rate of 7.5 mmol / g. cat ·It was measured to be less than h, showing significantly low catalytic performance.

[0217] Specifically, in the case of Manufacturing Example 2 in which no iron precursor was added, Manufacturing Example 3 in which citric acid was added after all metal precursors were added, or Manufacturing Examples 4 and 5 in which citric acid was added first, Comparative Examples 1 to 4 manufactured using the metal precursor powders exhibited very poor ammonia synthesis rates.

[0218] Precursor powder type (Co 1-x Fe x ) x value of Mo1O4 Ammonia synthesis rate (mmol / g) cat ·h) Example 1 Manufacturing Example 10.07511.8 Example 2 Manufacturing Example 80.059.5 Example 3 Manufacturing Example 90.112.4 Example 4 Manufacturing Example 100.12513.1 Example 5 Manufacturing Example 110.12516.6

[0219] Referring to Table 6 above, the ammonia synthesis catalysts of Examples 3 and 4, in which the x value was 0.1 to 0.125, showed a tendency for the ammonia synthesis rate to be somewhat improved compared to the ammonia synthesis catalysts of Examples 1 and 2. In addition, by introducing cesium (Co 1-x Fe x Cs z In Example 5, the ammonia synthesis catalyst precursor powder having a composition of )Mo1O4(x=0.125, z=0.1) was used, and the ammonia synthesis rate was 16.6 mmol / g. cat ·h, it showed the best ammonia synthesis efficiency among the catalysts of Examples 1 to 5.

[0220] Molal ratio of ammonia synthesis rate of ethylene glycol to citric acid (mmol / g) cat ·h) Example 1 Manufacturing Example 11.011.8 Example 6 Manufacturing Example 1206.8 Example 7 Manufacturing Example 130.59.0 Example 8 Manufacturing Example 142.05.6

[0221] As shown in Table 7 above, it was confirmed that a superior ammonia synthesis rate was exhibited when the molar ratio of ethylene glycol to citric acid satisfied a specific value. In particular, Examples 1 and 7, in which the molar ratio of ethylene glycol to citric acid was 0.5 to 1.5, exhibited superior ammonia synthesis rates.

[0222] As described above, the present invention has been described with specific details and limited examples and drawings, but these are provided only to help a more general understanding of the present invention, and are not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0223] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

Claims

1. Particles containing molybdenum (Mo), cobalt (Co) and iron (Fe) and having a pellet shape. X-ray diffraction (XRD) analysis results showed that the fourth peak intensity (I) at 2θ = 28.5 ± 0.2° 28.5° ) for the third peak intensity (I) at 2θ=26.5±0.2° 26.5° ) of the rain (I 26.5° / I 28.5° ) is 0.4 or more, a precursor for manufacturing an ammonia synthesis catalyst.

2. In paragraph 1, The above precursor is (Co 1-x Fe x )Mo1O4(0 <x<1)로 표시되는 것인 암모니아 합성 촉매 제조용 전구체.

3. In paragraph 2, A precursor for preparing an ammonia synthesis catalyst, wherein the above x is 0.05 to 0.

18.

4. In paragraph 1, The above precursor further includes cesium (Cs), (Co 1-x Fe x Cs z )Mo1O4(0 <x<1, 0.01≤z≤0.1)로 표시되는 것인 암모니아 합성 촉매 제조용 전구체.

5. In paragraph 4, A precursor for preparing an ammonia synthesis catalyst wherein z / x is 0.3 to 1.

0.

6. In paragraph 1, A precursor for preparing an ammonia synthesis catalyst, which exhibits a first peak at 2θ=14.5±0.2°, a second peak at 2θ=25.5±0.2°, a fifth peak at 2θ=32.7±0.2°, and a sixth peak at 2θ=44.0±0.2° as a result of X-ray diffraction (XRD) analysis.

7. An ammonia synthesis catalyst manufactured from a precursor for manufacturing an ammonia synthesis catalyst selected from any one of claims 1 to 6.

8. In paragraph 7, The above catalyst is (Co 1-x Fe x )Mo1N y (0 <x<1, 0.2<y<0.4)로 표시되는 암모니아 합성 촉매.

9. In paragraph 7, The above catalyst is (Co 1-x Fe x Cs z )Mo1N y (0 <x<1, 0.2<y<0.4, 0.01≤z≤0.1)로 표시되는 것인 암모니아 합성 촉매.

10. In paragraph 7, An ammonia synthesis catalyst, which, as a result of X-ray diffraction (XRD) analysis, exhibits a first peak at 2θ=32.5±0.2°, a second peak at 2θ=35.5±0.2°, a third peak at 2θ=40.0±0.2°, a fourth peak at 2θ=42.5±0.2°, and a fifth peak at 2θ=47.0±0.2°.

11. In paragraph 7, The above catalyst is an ammonia synthesis catalyst, which is a pellet having an average particle diameter of 0.1 mm to 10 mm.

12. In paragraph 7, The above catalyst is an ammonia synthesis catalyst comprising a plurality of pores.

13. In paragraph 12, An ammonia synthesis catalyst, wherein the volume occupied by pores having a pore size of 10 nm or more is 95% or more of the total pore volume of the catalyst.

14. A step for manufacturing a precursor for manufacturing a pellet-shaped ammonia synthesis catalyst; and A method for producing an ammonia synthesis catalyst, comprising an ammonolysis step of producing an ammonia synthesis catalyst by heat-treating the precursor for producing the above ammonia synthesis catalyst in an ammonia atmosphere.

15. In paragraph 14, The step of manufacturing a precursor for manufacturing an ammonia synthesis catalyst in the shape of a pellet is as follows: (S10) Step of introducing a molybdenum precursor and a cobalt precursor; (S20) Step of adding organic acid of C3-10; (S30) A step of preparing a precursor solution by introducing an iron precursor; (S40) A step of heating the precursor solution to prepare a precursor powder for preparing an ammonia synthesis catalyst; and (S50) A method for producing an ammonia synthesis catalyst, comprising a step of molding the precursor powder.

16. In paragraph 15, A method for producing an ammonia synthesis catalyst, wherein the molar ratio of the iron precursor to the total molar number of the iron precursor and cobalt precursor is 0.05 to 0.

3.

17. In paragraph 15, A method for producing an ammonia synthesis catalyst, further comprising a step of introducing a cesium (Cs) precursor into the precursor solution after the step (S30) and before the step (S40).

18. In paragraph 17, A method for producing an ammonia synthesis catalyst, wherein the molar ratio of the cesium precursor to the total moles of the iron precursor and the cesium precursor is 0.05 to 0.

1.

19. In paragraph 17, A method for producing an ammonia synthesis catalyst, wherein the above cesium (Cs) precursor introduction step is performed by a co-precipitation method.

20. In paragraph 15, A method for producing an ammonia synthesis catalyst, further comprising a step of adding a polyalcohol to the precursor solution after the step (S30) and before the step (S40).

21. In paragraph 20, A method for producing an ammonia synthesis catalyst, wherein the molar ratio of polyhydric alcohol to the organic acid is 0.1 to 2.

0.

22. In paragraph 15, The above step (S30) is a method for producing an ammonia synthesis catalyst performed by a co-precipitation method.

23. In paragraph 14, A method for producing an ammonia synthesis catalyst, wherein the above ammonolysis step is performed by heating the precursor for producing the ammonia synthesis catalyst at a temperature of 400°C to 800°C in an ammonia atmosphere.

24. Ammonia synthesis method using the ammonia synthesis catalyst of Article 7.

25. In paragraph 24, A method for synthesizing ammonia, which is performed under temperature conditions of 500°C or less.

26. In paragraph 24, A method for synthesizing ammonia, which is performed under pressure conditions of 50 bar or less.

27. In paragraph 24, Ammonia synthesis rate is 17 mmol / g cat ·Ammonia synthesis method of h or more.

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