Method for introducing silicon nitride(Si3N4) promoter to improve reactivity in mechanochemical ammonia synthesis

Abstract

According to one embodiment of the present invention, a mechanochemical ammonia synthesis method is provided, comprising the steps of: preparing a rotatable reaction vessel containing a plurality of balls (S100); introducing iron powder as a catalyst and silicon nitride powder as an accelerator into the reaction vessel (S200); introducing nitrogen gas into the reaction vessel (S300); rotating the reaction vessel for nitrogen decomposition (S400); introducing hydrogen gas into the reaction vessel after removing the nitrogen gas remaining in the reaction vessel (S500); and rotating the reaction vessel for ammonia synthesis (S600).

Description

Technology Field

[0001] The present invention relates to a method for mechanochemical ammonia synthesis, and more specifically, to a method for introducing a silicon nitride promoter to improve reactivity in mechanochemical ammonia synthesis. Background Technology

[0002] Ammonia (NH3) is an important compound playing a key role in efforts toward carbon neutrality. In particular, as it is utilized as a hydrogen storage and transport medium, it contributes to the essential energy transition for carbon neutrality alongside the growth of the hydrogen economy. Highlighted in various aspects as a green energy solution, ammonia is recognized as a core element in establishing sustainable industrial and energy systems. From this perspective, ammonia synthesis is recognized as one of the effective and critical technological solutions for realizing carbon neutrality, and its importance is increasingly being emphasized.

[0003] However, the conventional Haber-Bosch process for ammonia synthesis accounts for more than 2% of global energy consumption because it operates in a high-temperature and high-pressure environment (400-500°C, 200-300 bar). Since thermochemical environments require high equipment requirements and complex processes, there is a need for a method to efficiently synthesize ammonia under more relaxed conditions. Prior art literature

[0004] Korean Intellectual Property Office Published Patent Application No. 10-2023-0102614 (Published July 7, 2023) The problem to be solved

[0005] One objective of the present invention is to overcome the problem of increased reaction time required for ammonia synthesis due to the low reactivity between the iron catalyst and nitrogen and hydrogenation, which is the reaction determining step. means of solving the problem

[0006] According to one embodiment of the present invention, a mechanochemical ammonia synthesis method is provided, comprising the steps of: preparing a rotatable reaction vessel containing a plurality of balls (S100); introducing iron powder as a catalyst and silicon nitride powder as an accelerator into the reaction vessel (S200); introducing nitrogen gas into the reaction vessel (S300); rotating the reaction vessel for nitrogen decomposition (S400); introducing hydrogen gas into the reaction vessel after removing the nitrogen gas remaining in the reaction vessel (S500); and rotating the reaction vessel for ammonia synthesis (S600).

[0007] According to another aspect of the present invention, a mechanochemical ammonia synthesis apparatus is provided, comprising a plurality of balls and a rotatable reaction vessel receiving iron powder as a catalyst and silicon nitride powder as an accelerator, wherein nitrogen gas is introduced into the reaction vessel and the reaction vessel is rotated to decompose nitrogen, and hydrogen gas is introduced into the reaction vessel where the decomposed nitrogen remains and the reaction vessel is rotated to synthesize ammonia. Effects of the invention

[0008] According to one embodiment of the present invention, by adding silicon nitride as a promoter, the reactivity between the iron catalyst and the reaction gas can be improved.

[0009] According to one embodiment of the present invention, the sintering of an iron catalyst can be suppressed by adding silicon nitride as a promoter. Brief explanation of the drawing

[0010] Figure 1a is a field emission scanning electron microscope image showing the morphological characteristics analysis of hydrogenated iron powder. Figure 1b is a field emission scanning electron microscope image showing the elemental properties of the hydrogenated iron powder of Figure 1a. FIG. 1c is a field emission scanning electron microscope image showing the morphological characteristics of hydrogenated iron / silicon nitride powder used in a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Figure 1d is a field emission scanning electron microscope image showing the elemental characterization of the hydrogenated iron / silicon nitride powder of Figure 1c. FIG. 2 is a graph showing the ammonia yield of a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Figure 3 is a graph showing the amount of nitrogen gas decomposition according to the rotation speed of the reaction vessel in a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Figure 4 is a graph showing the amount of nitrogen gas decomposition over time in a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Specific details for implementing the invention

[0011] The above objectives, other objectives, features, and advantages will be easily understood through the following preferred embodiments associated with the accompanying drawings. However, the embodiments described herein are not limited to those described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete and that the technical concept is sufficiently conveyed to a person skilled in the art.

[0012] In describing each drawing, similar reference numerals have been used for similar components. In the attached drawings, the dimensions of the structures are depicted enlarged from their actual size for clarity of the invention. Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the invention, the first component may be named the second component, and similarly, the second component may be named the first component. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0013] In this specification, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "immediately above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "immediately below" the other part, but also the case where there is another part in between.

[0014] Unless otherwise specified, all numbers, values, and / or expressions used herein to represent amounts of ingredients, reaction conditions, polymer compositions, and formulations should be understood to be modified by the term “approximately” in all cases, as these numbers are essentially approximations reflecting the various uncertainties of measurement that occur in obtaining these values ​​among other things. Furthermore, where numerical ranges are disclosed herein, such ranges are continuous and, unless otherwise indicated, include all values ​​from the minimum value of such range to the maximum value including said maximum value. Moreover, where such ranges refer to integers, they include all integers from the minimum value to said maximum value including said maximum value, unless otherwise indicated.

[0016] A mechanochemical ammonia synthesis method according to one embodiment of the present invention may include the steps of: preparing a rotatable reaction vessel containing a plurality of balls (S100); introducing iron powder as a catalyst and silicon nitride powder as an accelerator into the reaction vessel (S200); introducing nitrogen gas into the reaction vessel (S300); rotating the reaction vessel for nitrogen decomposition (S400); introducing hydrogen gas into the reaction vessel after removing the nitrogen gas remaining in the reaction vessel (S500); and rotating the reaction vessel for ammonia synthesis (S600).

[0018] According to one embodiment of the present invention, a plurality of balls and a reaction vessel may be made of hardened steel.

[0020] According to one embodiment of the present invention, in the step (S300) of introducing nitrogen gas into the reaction vessel, the pressure of the nitrogen gas inside the reaction vessel may be 9 bar. By controlling the pressure of the nitrogen gas inside the reaction vessel, the effect of controlling the amount of nitrogen adsorption can be obtained. The higher the pressure of the nitrogen gas, the greater the amount of nitrogen adsorption. In particular, in the two-stage process used in one embodiment of the present invention, it is advantageous for the nitrogen pressure to be higher.

[0022] According to one embodiment of the present invention, in the step (S500) of removing the nitrogen gas remaining in the reaction vessel and then introducing hydrogen gas into the reaction vessel, the pressure of the hydrogen gas in the reaction vessel may be 9 bar. By controlling the pressure of the hydrogen gas in the reaction vessel, the effect of controlling the amount of ammonia produced can be obtained. The higher the pressure of the hydrogen gas, the greater the amount (mol) of ammonia produced.

[0024] According to one embodiment of the present invention, in the step (S400) of rotating the reaction vessel for nitrogen decomposition, the rotation speed of the reaction vessel may be 400 to 450 rpm. By controlling the rotation speed of the reaction vessel, the effect of controlling the yield of the nitrogen decomposition reaction can be obtained. If the rotation speed exceeds the upper limit of the above range, there is a disadvantage that the nitrogen decomposition rate is reduced because the excessive heat generated hinders the progress of the nitrogen decomposition reaction, since the nitrogen decomposition reaction is an exothermic reaction. If the rotation speed falls below the lower limit of the above range, there is a disadvantage that nitrogen decomposition becomes difficult because sufficient kinetic energy is not generated.

[0026] According to one embodiment of the present invention, the reaction vessel may be rotated for 30 to 60 minutes and then rested for 10 minutes. By controlling the rotation time of the reaction vessel, the effect of controlling the yield of the nitrogen decomposition reaction can be obtained. As the total rotation time of the reaction vessel increases during the nitrogen decomposition step, the amount of nitrogen decomposition may increase. If the rotation time exceeds the upper limit of the above range, there is a disadvantage that excessive heat is generated, causing the nitrogen decomposition rate to decrease.

[0028] According to one embodiment of the present invention, in the step (S600) of rotating the reaction vessel for ammonia synthesis, the rotation speed of the reaction vessel may be 500 rpm. By controlling the rotation speed of the reaction vessel, the effect of controlling the yield of the ammonia synthesis reaction can be obtained. The higher the rotation speed, the greater the amount of ammonia produced.

[0030] According to one embodiment of the present invention, the reaction vessel may be rotated for 60 minutes and then rested for 10 minutes. Additionally, the total rotation time of the reaction vessel may be 2 to 4 hours. By controlling the total rotation time of the reaction vessel, the effect of controlling the yield of the ammonia synthesis reaction can be obtained. Since the batch method used in one embodiment of the present invention is not a continuous process, it is necessary to set an appropriate total rotation time. If the total rotation time exceeds the upper limit of the above range, there is a disadvantage that the generated ammonia may be decomposed again.

[0032] A mechanochemical ammonia synthesis apparatus according to another aspect of the present invention comprises a plurality of balls and a rotatable reaction vessel that accommodates iron powder as a catalyst and silicon nitride powder as an accelerator, wherein nitrogen gas is introduced into the reaction vessel and the reaction vessel is rotated to decompose nitrogen, and ammonia can be synthesized by introducing hydrogen gas into the reaction vessel in which the decomposed nitrogen remains and rotating the reaction vessel.

[0034] According to one embodiment of the present invention, the rotation speed of the reaction vessel for nitrogen decomposition can be maintained at 400 to 450 rpm.

[0036] According to one embodiment of the present invention, the rotation of the reaction vessel may be performed for 30 to 60 minutes, followed by a rest for 10 minutes. Additionally, the total rotation time of the reaction vessel may be 2 to 4 hours.

[0038] According to one embodiment of the present invention, the rotation speed of the reaction vessel for ammonia synthesis can be maintained at 500 rpm.

[0040] According to one embodiment of the present invention, the rotation of the reaction vessel may be rotated for 60 minutes and then rested for 10 minutes.

[0042] The present invention will be explained in more detail through the following examples. The following examples are merely illustrative to aid in understanding the present invention and do not limit the scope of the invention.

[0044] [Examples and Comparative Examples]

[0045] - Examples

[0046] High-purity silicon nitride powder (β-Si3N4, predominantly β-phase, ≤10 micron primary particle size, Sigma-Aldrich) and iron powder (iron sponge, ~100 mesh, 99.9% metals basis, Alfa Aesar) were used. The gases used in the reaction were high-purity nitrogen (N2, 99.999%, KOSEM Corp.) and hydrogen (H2, 99.999%, Daesung Industrial Gases Co.). A planetary ball-milling machine (Pulverisette 6, Fritsch) was used as the equipment for the mechanochemical experiment, and hardened steel containers and balls were used.

[0047] The experimental procedure is as follows.

[0048] 12.0 g of iron and 0.9 g of silicon nitride are placed in a container under an Ar atmosphere and sealed. Then, 9 bar of nitrogen gas is injected. Nitrogen decomposition is performed at 450 rpm at intervals of 30 min / 10 min. Subsequently, to synthesize ammonia, the remaining nitrogen gas in the container is completely removed, and then 9 bar of hydrogen gas is injected. Milling is performed at 500 rpm at intervals of 60 min / 10 min. Finally, the concentration of the synthesized ammonia is checked using gas chromatography (GC).

[0049] - Comparative Example 1

[0050] Ammonia was synthesized using the same apparatus and procedure as in the above example, except that silicon nitride powder was used and only iron powder was used.

[0051] - Comparative Example 2

[0052] Ammonia was synthesized using the same apparatus and procedure as in the above example, except that silicon carbide (SiC) was used instead of silicon nitride powder.

[0053] - Comparative Example 3

[0054] Ammonia was synthesized using the same apparatus and procedure as in the above example, except that silicon dioxide (SiO2) was used instead of silicon nitride powder.

[0056] [Experimental Example]

[0057] FIG. 1a is a field emission scanning electron microscope image showing the morphological characteristics of hydrogenated iron powder, and FIG. 1b is a field emission scanning electron microscope image showing the elemental characteristics of the hydrogenated iron powder of FIG. 1a. FIG. 1c is a field emission scanning electron microscope image showing the morphological characteristics of hydrogenated iron / silicon nitride powder used in a mechanochemical ammonia synthesis method according to one embodiment of the present invention, and FIG. 1d is a field emission scanning electron microscope image showing the elemental characteristics of the hydrogenated iron / silicon nitride powder of FIG. 1c.

[0059] Specifically, FIGS. 1a and 1b are field emission scanning electron microscope images of the iron powder used in Comparative Example 1, and FIGS. 1c and 1d are field emission scanning electron microscope images of the silicon nitride / iron powder used in the Example.

[0061] Referring to Fig. 1a, it can be seen that the iron particles are clustered after hydrogenation. This indicates that the active sites of the iron catalyst have been reduced. Additionally, referring to Fig. 1b, it can be confirmed that the catalyst is mostly composed of iron and contains some adsorbed nitrogen.

[0062] In contrast, referring to Fig. 1c, it can be seen that the size of the iron particles after hydrogenation is relatively small. This confirms that silicon nitride increases the surface area of ​​the iron catalyst and maintains the active sites. Additionally, referring to Fig. 1d, it can be seen that silicon nitride is evenly distributed on the iron catalyst.

[0064] FIG. 2 is a graph showing the ammonia yield of a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Specifically, ammonia yields were obtained from various silicon-based catalysts added at the same loading amount (3.0 at%). Nitrogen dissociation was performed at 9 bar for 20 hours, followed by hydrogenation at 9 bar for 3 hours.

[0066] Referring to FIG. 2, the ammonia yields synthesized in the Example and Comparative Examples 1 to 3 are compared. In Comparative Example 1, 2.1 mmol was obtained, in Comparative Example 2, 1.8 mmol was obtained, and in Comparative Example 3, 8.8 mmol was obtained. In contrast, in the Example, 11.9 mmol was obtained. As such, it can be seen that the ammonia yield according to the Example of the present invention is superior to that of the Comparative Examples.

[0068] FIG. 3 is a graph showing the amount of nitrogen gas decomposed according to the rotation speed of the reaction vessel in a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Specifically, the amount of decomposed nitrogen gas was obtained as a function of the rotation speed of the reaction vessel after a total of 240,000 rotation cycles.

[0070] Referring to FIG. 3, the amount of nitrogen gas decomposition in the Example and Comparative Example 1 is compared. The amount of nitrogen gas decomposition according to the Example was greater than the amount of nitrogen gas decomposition according to Comparative Example 1. Thus, it can be seen that according to the Example of the present invention, the decomposition of nitrogen gas is carried out more effectively than in Comparative Example 1.

[0072] FIG. 4 is a graph showing the amount of nitrogen gas decomposition over time in a mechanochemical ammonia synthesis method according to one embodiment of the present invention. Specifically, the amount of nitrogen gas decomposition over time was obtained by rotating the reaction vessel at 450 rpm for ball-milling.

[0074] Referring to FIG. 4, the amount of nitrogen gas decomposition in the Example and Comparative Example 1 is compared. According to the Example, nitrogen gas adsorption shows a linear dependence on ball-milling time. In contrast, according to Comparative Example 1, it can be seen that nitrogen gas decomposition has a linear relationship with the natural logarithm of ball-milling time.

Claims

Claim 1 A mechanochemical ammonia synthesis method comprising the steps of: preparing a rotatable reaction vessel containing a plurality of balls (S100); introducing iron powder as a catalyst and silicon nitride powder as a promoter into the reaction vessel (S200); introducing nitrogen gas into the reaction vessel (S300); rotating the reaction vessel for nitrogen decomposition (S400); introducing hydrogen gas into the reaction vessel after removing the nitrogen gas remaining in the reaction vessel (S500); and rotating the reaction vessel for ammonia synthesis (S600). Claim 2 A mechanochemical ammonia synthesis method according to claim 1, wherein in the step (S300) of introducing nitrogen gas into the reaction vessel, the pressure of the nitrogen gas inside the reaction vessel is 9 bar. Claim 3 A mechanochemical ammonia synthesis method according to claim 1, wherein in the step (S500) of removing nitrogen gas remaining in the reaction vessel and then introducing hydrogen gas into the reaction vessel, the pressure of the hydrogen gas inside the reaction vessel is 9 bar. Claim 4 A mechanochemical ammonia synthesis method according to claim 1, wherein in the step (S400) of rotating the reaction vessel for nitrogen decomposition, the rotation speed of the reaction vessel is 400 to 450 rpm. Claim 5 A mechanochemical ammonia synthesis method according to claim 4, wherein the rotation of the reaction vessel is performed for 30 to 60 minutes followed by a rest for 10 minutes. Claim 6 A mechanochemical ammonia synthesis method according to claim 1, wherein in the step (S600) of rotating the reaction vessel for ammonia synthesis, the rotation speed of the reaction vessel is 500 rpm. Claim 7 A mechanochemical ammonia synthesis method according to claim 6, wherein the rotation of the reaction vessel is performed by rotating for 60 minutes followed by resting for 10 minutes. Claim 8 A mechanochemical ammonia synthesis apparatus comprising a plurality of balls and a rotatable reaction vessel containing iron powder as a catalyst and silicon nitride powder as an accelerator, wherein nitrogen gas is introduced into the reaction vessel and the reaction vessel is rotated to decompose nitrogen, and hydrogen gas is introduced into the reaction vessel where the decomposed nitrogen remains and the reaction vessel is rotated to synthesize ammonia. Claim 9 A mechanochemical ammonia synthesis apparatus according to claim 8, wherein the rotational speed of the reaction vessel for nitrogen decomposition is maintained at 400 to 450 rpm. Claim 10 A mechanochemical ammonia synthesis apparatus according to claim 9, wherein the rotation of the reaction vessel is performed for 30 to 60 minutes followed by a rest for 10 minutes. Claim 11 A mechanochemical ammonia synthesis apparatus according to claim 8, wherein the rotational speed of the reaction vessel for ammonia synthesis is maintained at 500 rpm. Claim 12 A mechanochemical ammonia synthesis apparatus according to claim 11, wherein the rotation of the reaction vessel is such that it rotates for 60 minutes followed by a rest for 10 minutes.

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