Borohydride and method for producing sheet thereof

Abstract

To provide a method for producing borohydride and its sheet from hydrogen and boron by a relatively simple method.SOLUTION: The method for producing a hydrogen boride and a sheet thereof is characterized in that boron fine particles 21, an atmospheric pressure plasma generator 27, and a working gas containing hydrogen are used as main components, at least hydrogen is supplied to the atmospheric pressure plasma generator 27 as the working gas of the atmospheric pressure plasma generator 27, and the boron fine particles 21 are irradiated with atmospheric pressure plasma to produce a hydrogen boride 7 and a hydrogen boride sheet 8 which is a sheet thereof. Preferably, boron fine particles are added to the working gas. More preferably, it is desirable that a stirrer and a dish are added to the container, and the container is disposed so that the boron fine particles placed in the dish are irradiated with the atmospheric pressure plasma.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing borohydride and sheets thereof, and more particularly to a method for relatively simply producing borohydride, a compound of hydrogen and boron, and sheets thereof using atmospheric pressure plasma. [Background technology]

[0002] The arrival of a hydrogen-based society is expected to be a reality in the near future, making hydrogen carriers essential for safe transportation. Hydrogen carriers include liquid hydrogen, organic hydrides, ammonia, and formic acid. Liquid hydrogen is transported by liquefying hydrogen at -253°C, but evaporation reduces inventory by 12% each month. Ammonia is considered the most promising hydrogen carrier, but it is a hazardous substance and can cause disasters if handled improperly. It also consumes a large amount of energy during production. The organic hydride method adds toluene to hydrogen to produce methylcyclohexane, which can be transported. However, the disadvantages are the need to transport the toluene to a hydrogenation site and the need to heat the hydrogen to 300–350°C. Formic acid can also be used to extract high-pressure hydrogen by adding hydrogen to carbon dioxide, but the release of carbon dioxide is a drawback.

[0003] Meanwhile, in 2017, a research team including the Tokyo Institute of Technology succeeded in synthesizing a boron-hydrogen sheet from boron and hydrogen. They found that irradiating this boron-hydrogen sheet with ultraviolet light released 8% of its mass of hydrogen. The mass hydrogen density of the hydrogen storage alloy was 2% compared to 6.2% for methylcyclohexane and 4.4% for formic acid. Of these, boron-hydrogen had the highest value, demonstrating its superiority as a hydrogen carrier.

[0004] It has been discovered that this borohydride can release hydrogen even when electrically powered at room temperature and pressure. Because it is a solid, it can be transported in containers. Furthermore, while ammonia, formic acid, and methylcyclohexane are difficult to handle due to their toxicity and corrosiveness, borohydride is highly safe at room temperature and pressure. Furthermore, because it allows for the safe storage of explosive hydrogen using low energy, borohydride and borohydride sheets are expected to be lightweight and safe hydrogen carriers.

[0005] However, to synthesize this borohydride, magnesium diboride is dissolved in methanol or acetonitrile, and converted to magnesium and diboride using an ion exchange resin while hydrogen is blown in. The mixture is then stirred in nitrogen and the filtrate is dried to obtain borohydride. As the process is complicated and requires an ion exchange resin, it is not easy to obtain borohydride. Therefore, there is a need for a relatively simple method for synthesizing borohydride and its precursors from hydrogen and boron. [Prior art documents] [Patent documents]

[0006] [Non-Patent Document 1] "Formation and characterization of hydrogen boride sheets derived from MgB2 by cation exchange" in the Journal of the American Chemical Society, September 19, 2017 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to develop a method for producing borohydride and its sheets from hydrogen and boron in a relatively simple manner. [Means for solving the problem]

[0008] In order to solve the problem, the invention of claim 1 is a method for producing hydrogen boride and a sheet thereof, which comprises boron microparticles, an atmospheric pressure plasma generator, and a working gas containing hydrogen as its main elements, and is characterized in that at least hydrogen is supplied to the atmospheric pressure plasma generator as the working gas for the atmospheric pressure plasma generator, and the generated atmospheric pressure plasma is irradiated onto the boron microparticles to produce hydrogen boride and a sheet thereof.

[0009] The invention of claim 2 is characterized in that in the method for manufacturing borohydride and a sheet thereof according to claim 1, the working gas is at least one selected from the group consisting of water, hydrogen, helium, neon, argon, krypton, xenon, radon, nitrogen, and carbon dioxide.

[0010] The invention of claim 3 is characterized in that in the method for manufacturing borohydride and a sheet thereof according to claim 1 or 2, boron fine particles are added to the working gas.

[0011] The invention of claim 4 is characterized in that, in the method for manufacturing boron hydride and sheets thereof described in any one of claims 1 to 3, a stirrer and a dish are added to the container, the boron microparticles are placed in the dish, and the dish is arranged so that the atmospheric pressure plasma is irradiated while stirring. [Effects of the Invention]

[0012] The method for producing borohydride of the present invention has the following effects. 1 Hydrogen borate can be produced relatively easily using an atmospheric pressure plasma generator. 2. Borohydride and its sheets can be produced relatively easily, even in small quantities. 3. Hydrogen borate and its sheets can be produced using extremely little energy. 4. There are few moving parts, so production can be done very quietly. 5. Compared to conventional techniques, no solution is used, so there is no need for filtration and drying. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a conventional manufacturing process of a borohydride sheet. [Figure 2] 1 is a schematic diagram showing a method for manufacturing borohydride and a sheet thereof according to an embodiment of the present invention (Example 1). [Figure 3] 1 is a schematic diagram showing a method for producing borohydride and a sheet thereof in accordance with an embodiment of the present invention, in which the stirrer and the dish are added to the method in accordance with the embodiment 1 (Example 2). DETAILED DESCRIPTION OF THE INVENTION

[0014] This method for producing boron boride and a sheet thereof comprises boron microparticles, an atmospheric pressure plasma generator, and a working gas containing hydrogen, and is characterized in that at least hydrogen is supplied as the working gas to the atmospheric pressure plasma generator, and the boron microparticles are irradiated with the generated atmospheric pressure plasma to produce boron boride and a sheet thereof. Preferably, the working gas is at least one selected from the group consisting of water, hydrogen, helium, neon, argon, krypton, xenon, radon, nitrogen, and carbon dioxide. It is also preferred that boron microparticles be added to the working gas. More preferably, a stirrer and a dish are added to the container, and the boron microparticles placed in the dish are placed in such a way that the atmospheric pressure plasma is irradiated while stirring.

[0015] Here, we will discuss atmospheric pressure plasma. Atmospheric pressure plasma is plasma generated under atmospheric pressure and is also known as low-temperature plasma. Generally, the lower the pressure at which plasma is generated, the lower the voltage required, the longer the mean free path, and the easier it is to control the plasma.

[0016] Atmospheric pressure plasma is suitable for continuous processing, resulting in high productivity, and does not require a vacuum device, resulting in low processing costs and requiring a simple device configuration. Atmospheric pressure plasma can be generated by methods such as corona discharge, dielectric barrier discharge, RF discharge, microwave discharge, and arc discharge, and can be easily generated using gases such as Ar and He.

[0017] Here, we will discuss the method for producing borohydride described in Non-Patent Document 1. Figure 1 is a schematic diagram showing a conventional method for producing borohydride. In Figure 1, 1 is magnesium diboride, 2 is methanol or acetonitrile, 3 is ion exchange resin, 4 is a vessel, 5 is a stirrer, 6 is a nitrogen atmosphere, 7 is borohydride, 8 is a borohydride sheet, and 9 is a dried filtrate.

[0018] A research group including researchers from the University of Tsukuba focused on a material called magnesium diboride 1 as a base material for creating hydrogen boride sheets 8. Within the material, boron forms a planar structure with strong covalent bonds known as sp2 hybrid orbitals. Magnesium diboride 1 is a material in which the honeycomb structure of this boron carries a negative charge and positive magnesium ions exist between the boron framework. The group exchanged the positive magnesium ions in magnesium diboride 1 with positive hydrogen ions (protons), transforming the layered three-dimensional structure into a loose sheet structure, and succeeded in creating hydrogen boride sheets 8, which are made up of linked hydrogen borides 7.

[0019] Figure 1 is a schematic diagram of the conventional procedure for producing borohydride sheets 8. In a nitrogen atmosphere 6 at atmospheric pressure, magnesium diboride 1 and ion exchange resin 3 are mixed in a container 4 containing room-temperature methanol or acetonitrile 2 and stirred with a stirrer 5. The precipitate is then removed and dried to obtain a dried filtrate 9. Yellow powdery borohydride sheets 8 are obtained with an average yield of 42.3%. Because the magnesium contained in the starting material is recovered by the ion exchange resin 3 during the ion exchange process, no Mg is present in this sheet material. Consequently, it was revealed that borohydride sheets 8 with a composition ratio of H:B of 1:1 are formed through the ion exchange reaction represented by the reaction formula MgB2 + 2H+ → Mg2+ + 2HB.

[0020] However, the manufacturing process to obtain the hydrogen boride sheet 8 is very complicated and not suitable for mass production, so there is a need for a method to manufacture hydrogen boride 7 and hydrogen boride sheet 8 that can be synthesized relatively easily.In the present invention, hydrogen boride 7, which is the key to hydrogen carriers, and its sheet, hydrogen boride sheet 8, are synthesized relatively easily from hydrogen and boron for the purpose of mass production. [Example]

[0021] 2 is a schematic diagram showing a method for manufacturing borohydride and its sheet in one embodiment of the present invention. (Example 1) The explanation will be based on Figure 2. In Figure 2, 21 is boron microparticles, 24 is an observation window, 25 is an access port, 26 is a working gas recovery port, 27 is an atmospheric pressure plasma generator, 28 is a plasma jet, 29 is a ground electrode, 30 is a high-voltage electrode, 31 is a low-frequency high-voltage power supply, 32 is earth, 33 is an argon cylinder, 34 is a hydrogen cylinder, 35 is a working gas recovery, separation, and purification device, 36 is a valve, 37 is a pipe, and 38 is an argon atmosphere. 4, 7, and 8 are the same as in Figure 1. Container 4 is provided with an observation window 24, an access port 25, and a working gas recovery port 26, and an argon atmosphere 38 is created inside container 4. Boron microparticles 21 and an atmospheric pressure plasma generator 27 are placed inside container 4, and a plasma jet 28, a ground electrode 29, a high-voltage electrode 30, a low-frequency high-voltage power supply 31, and a ground 32 are connected to atmospheric pressure plasma generator 27. In addition, working gas recovery, separation, and purification device 35 is connected to working gas recovery port 26, and used working gases, Ar and H2, are separated and purified, and then connected to pipe 37 through valve 36. An argon cylinder 33 and a hydrogen cylinder 34 are connected to a pipe 37 through a valve 36 .

[0022] The device is configured as shown in Figure 2. By supplying electricity externally to a low-frequency, high-voltage power supply 31, a high voltage is generated at the ground electrode 29 and the high-voltage electrode 30. Argon gas from an argon cylinder 33 and hydrogen gas from a hydrogen cylinder 34 are supplied as working gases to an atmospheric-pressure plasma generator 27, and argon and hydrogen are released in a plasma state as the plasma jet 28. The boron particles 21 at the tip of the plasma jet 28 react with the boron particles 21 to form hydrogen boride 7, and as the reaction progresses, much of the hydrogen boride 7 becomes hydrogen boride sheet 8. Therefore, the vessel 4 contains a mixture of boron particles 21, hydrogen boride 7, and hydrogen boride sheet 8. To increase the production rate of the hydrogen boride sheet 8, the unreacted boron particles 21 are activated over time by the action of atmospheric-pressure plasma to synthesize hydrogen boride 7, which then self-assembles to form the hydrogen boride sheet 8.

[0023] It should be noted that the hydrogen release efficiency of both boron boride 7 and boron boride sheet 8 is higher with boron boride sheet 8, but it is also more expensive. On the other hand, boron boride 7 is less expensive and, as mentioned above, can be produced relatively easily. Since using only boron boride sheet 8 is extremely costly, if used as a hydrogen carrier, there is no problem with a mixture of boron boride 7 and boron boride sheet 8. The mixture described above allows the use of both boron boride 7 and boron boride sheet 8 as hydrogen carriers at a lower cost. Needless to say, it is preferable to use only boron boride sheet 8 as a hydrogen carrier. Furthermore, by implementing the present invention, boron boride 7 alone may be used as a hydrogen carrier.

[0024] In addition, although argon and hydrogen are used as the working gas in Example 1, other working gases may be used instead of argon. For example, when helium is used as the working gas together with hydrogen, helium is more stable as a plasma and better results can be obtained. However, helium is currently a very expensive substance, so if financial resources are available, helium may be used.

[0025] It is also possible to put the boron microparticles 21 into the pipe 37 of the atmospheric pressure plasma generator 27 and activate them in the atmospheric pressure plasma generator 27 or in the plasma jet 28 to produce boron hydride 7 and boron hydride sheet 8. In this case, since the boron is a solid, it is best to use nanoparticles.

[0026] When water is used as the working gas, the water is heated and sent to the atmospheric pressure plasma generator 27 in the form of steam, which turns it into plasma and generates hydrogen. Therefore, even if hydrogen is not sent to the atmospheric pressure plasma generator 27 as a working gas, hydrogen is generated when the steam turns into plasma, and this hydrogen and the boron microparticles 21 are used to produce hydrogen boride 7 and hydrogen boride sheet 8.

[0027] This section compares the hydrogen adsorption characteristics and manufacturing costs of borohydride 7 and borohydride sheet 8. Because borohydride sheet 8 has a two-dimensional thin film structure, it has a large specific surface area, allowing for efficient chemical adsorption of hydrogen. The hydrogen adsorption capacity is reported to be approximately 5.2 wt%. On the other hand, because borohydride 7 has a three-dimensional structure, its specific surface area is not as large as that of a two-dimensional nanosheet. However, the specific surface area increases when it is nano-sized, and the hydrogen adsorption capacity is estimated to be approximately 3.5 wt%. Even from this, while borohydride sheet 8 has a greater hydrogen adsorption capacity, both borohydride 7 and borohydride sheet 8 can be used as hydrogen carriers without any problems, even when mixed with borohydride 7.

[0028] FIG. 3 is a schematic diagram showing a method for producing borohydride and a sheet thereof, in which the stirrer and the plate are added to Example 1, in accordance with one embodiment of the present invention. This is Example 2. Regarding FIG. 3, reference numeral 39 denotes a plate, 40 denotes a magnetic stirrer, and 41 denotes a magnetic stirrer. Reference numerals 4, 21, 24-38 are the same as those in FIG. 2. FIG. 3 is a schematic diagram showing a method for producing borohydride and a sheet thereof, in which the stirrer and the plate are added. In FIG. 1, borohydride particles 21 at the bottom of container 4 are irradiated with plasma jet 28 from atmospheric pressure plasma device 27 to produce borohydride 7 and borohydride sheet 8. However, if the plasma jet 28 is irradiated onto borohydride particles 21 at the bottom of container 4, the reaction only affects the surface of borohydride particles 21, leaving the borohydride particles 21 located below them unaffected, resulting in reduced efficiency. Therefore, in order to uniformly irradiate the boron hydrogen particles 21 with the plasma jet 28 and produce the products, hydrogen boride 7 and hydrogen boride sheet 8, a magnetic stirrer 40 and a magnetic stirrer 41 are added to stir the boron particles 21 in the dish 39, and the magnetic stirrer 40 is slowly rotated to stir the boron particles 21 and produce more of the hydrogen boride sheet 8. In this way, the hydrogen boride sheet 8 can be efficiently produced from the hydrogen boride particles 21.

[0029] The agitator may be any type that can agitate the boron microparticles that have been added. There are various types of agitators, such as agitators that use a rotating propeller to agitate the boron microparticles placed in the dish, and agitators that tilt the rotation axis of the dish and rotate the dish to agitate the boron microparticles placed in the dish. However, the key is that any agitator can be used as long as it can agitate the boron microparticles. [Industrial Applicability]

[0030] This invention suggests that boron hydride and boron hydride sheets have the potential to become the most convenient substances to use as necessary hydrogen carriers in the hydrogen society of the near future, and it is expected that boron hydride and boron hydride sheets will be widely used and developed as key players in the hydrogen society. [Explanation of symbols]

[0031] 1. Magnesium diboride 2. Methanol or acetonitrile 3. Ion exchange resin 4 containers 5. Mixer 6 Nitrogen atmosphere 7. Borohydride 8. Borohydride Sheet 9 Dried filtrate 21 Boron particles 24 Observation window 25 Work entrance 26 Working gas recovery port 27 Atmospheric pressure plasma generator 28 Plasma Jet 29 Ground electrode 30 High Voltage Electrode 31 Low frequency high voltage power supply 32 Earth 33 Argon Cylinder 34 Hydrogen Cylinder 35 Working gas recovery, separation and purification equipment 36 Valve 37 Pipe 38 Argon atmosphere 39 plates 40 Magnetic Stir Bar 41 Magnetic Stirrer

Claims

1. A method for producing hydrogen boride and a sheet thereof, comprising as its main elements boron microparticles, an atmospheric pressure plasma generator, and a working gas containing hydrogen, the method comprising supplying at least hydrogen as the working gas of the atmospheric pressure plasma generator to the atmospheric pressure plasma generator, and irradiating the generated atmospheric pressure plasma onto the boron microparticles to produce hydrogen boride and a sheet thereof.

2. 2. The method for producing borohydride and a sheet thereof according to claim 1, wherein the working gas is at least one selected from the group consisting of water, hydrogen, helium, neon, argon, krypton, xenon, radon, nitrogen, and carbon dioxide.

3. 3. The method for producing borohydride and a sheet thereof according to claim 1 or 2, wherein boron fine particles are added to the working gas.

4. 4. The method for producing boron hydride and a sheet thereof according to any one of claims 1 to 3, further comprising adding a stirrer and a dish to the container, placing the boron microparticles in the dish, and irradiating the dish with atmospheric pressure plasma while stirring.

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