Hydrogen storage fuel and production method of the same

Abstract

To provide a hydrogen storage fuel improved in handling safety and in a form suitable for storage and transportation.SOLUTION: The hydrogen storage fuel is composed by confining ammonia (NH3), which constitutes a hydrogen storage medium in the form of a solid cubic crystal, within a borate glass matrix of (B2O3-B(OH)3). The hydrogen storage medium is produced by preparing a mixed aqueous solution in which boric acid (B3O2) is mixed with an aqueous solution in which ammonia (NH3) is dissolved, freezing the mixed aqueous solution to prepare a frozen solid, freeze-drying the frozen solid, discharging water vapor (H2O) contained as gas and a boron compound (BHO) contained as gas in the frozen solid, concentrating ammonia (NH3) in the frozen solid, and confining ammonia (NH3) as a solid cubic crystal within a borate glass matrix (B2O3-B (OH) 3) at normal temperature and pressure.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a hydrogen storage fuel using ammonia, which is a hydrogen-containing compound, and a method for producing the hydrogen storage fuel. [Background technology]

[0002] Traditionally, there has been a demand to reduce carbon dioxide emissions in order to prevent environmental destruction. In order to reduce carbon dioxide emissions, efforts are being made to supply renewable energy (natural energy) using solar and wind power generation. However, these natural energies have some limitations. In other words, electricity from solar and wind power generation depends on the weather, making it difficult to provide a stable supply that matches demand. In addition, there are geographical limitations to installing facilities. Therefore, it is necessary to develop storage technology so that natural energy can be used when needed. One of the most promising storage technologies is the production of hydrogen through water electrolysis. Hydrogen can be converted into electricity using fuel cells, and can also be burned directly as an alternative to fossil fuels. However, gaseous hydrogen has a low energy density due to its large volume, making it difficult to store and transport. In addition, liquid hydrogen needs to be stored by cooling it to below 20K, which is a cost problem.

[0003] Therefore, as a hydrogen storage material that can solve the problems associated with gaseous hydrogen, we have developed a hydrogen storage material that has a high content density per volume and mass and does not emit carbon dioxide (CO) when burned. 2 Ammonia, a hydrogen-containing compound that does not emit CO2, has been attracting attention. Ammonia becomes liquid at 298K and approximately 8 atm, so it can be stored in a cylinder as a liquid at room temperature. It is expected that ammonia can be used directly as fuel for ammonia power generation and ammonia engines.

[0004] Ammonia can be synthesized on a large scale from atmospheric nitrogen and hydrogen using iron as a catalyst at high temperature and pressure by the Haber-Bosch process, which has led to the mass production of fertilizer to increase food production. In addition, a method has been developed to synthesize ammonia at low pressure by improving the Haber-Bosch process and using lithium (Li) compounds as a catalyst. Furthermore, research is being conducted on the generation of ammonia on a small scale using ubiquitous natural energy. That is, nitrogen gas (N 2 As a method for cleaving the strong NN bond in (g)) to produce ammonia, methods using electric fields, discharge, and surface plasmon resonance of a catalyst are being investigated.

[0005] The reverse reaction of the above can be carried out by using a suitable catalyst, such as nickel (Ni), zeolite, calcium hydrogen nitrite (Ca 2 When ammonia is converted to hydrogen gas (H 2 (g)) and nitrogen gas (N 2 (g)) and hydrogen (H 2 ) can be collected.

[0006] Ammonia produced from hydrogen using natural energy-based water electrolysis and atmospheric nitrogen is called green ammonia. Green ammonia is expected to be an alternative energy source to fossil fuels, and is attracting attention as a fuel for internal combustion engines and power generation systems.

[0007] As an alternative method for synthesizing ammonia to the Haber-Bosch process, the method described in Patent Document 1 has been proposed.

[0008] Patent Document 2 discloses an ammonia engine system that uses ammonia as fuel. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2014 / 115582 Brochure [Patent Document 2] International Publication No. 2010 / 058807 Brochure Summary of the Invention [Problem to be solved by the invention]

[0010] Incidentally, when liquid ammonia filled in a cylinder is ejected, it immediately vaporizes and becomes gaseous ammonia. Gaseous ammonia can easily be inhaled into the body, irritating the mucous membranes of the respiratory organs and causing shock, which can lead to respiratory arrest. When inhaled into the body, it can increase the ammonia concentration in the body's blood, which can lead to impaired consciousness. Also, if it gets into the eyes, it can cause eye damage.

[0011] As described above, gaseous ammonia is a substance that is extremely harmful to living organisms, and is difficult to store, manage, and transport, making it difficult to use it as a widely applicable energy carrier.

[0012] In addition, when ammonia is cooled to 195.5K or less under normal pressure, it becomes a stable solid, its sublimation vapor pressure is reduced to 0.0609 bar, and it becomes odorless. Therefore, by being a stable solid at room temperature, ammonia can be safely stored and transported as a storage material for hydrogen, which is expected to be a new energy source.

[0013] Therefore, an object of the present invention is to provide a new hydrogen storage fuel that can solve the problems associated with ammonia, which is a hazardous substance to living organisms, difficult to store, and difficult to transport.

[0014] A further technical object of the present invention is to provide a hydrogen storage fuel that can be used safely and is in a form suitable for storage and transportation.

[0015] Furthermore, other technical objects of the present invention will become more apparent from the following description with reference to the drawings. [Means for solving the problem]

[0016] The present invention is a novel solid hydrogen storage fuel that was completed as a result of intensive research by the present inventors in order to solve the above-mentioned technical problems. 3 ) as a solid cubic crystal in a borate glass matrix (B 2 O 3 -B(OH) 3 ) that is trapped inside.

[0017] By the way, ammonia (NH 3 ) has a triple point temperature (T) of 195.5K and a pressure (p) of 0.0609 bar, as shown in the phase diagram in Figure 1. As shown in this phase diagram, ammonia (NH 3 ) is a solid cubic (NH 3 )(cr)) can exist stably as a cubic ammonia (cubic-(NH 3 )(cr)) exists as fine particles.

[0018] In addition, ammonia (NH 3 ) cannot exist in a solid form at room temperature and pressure, as shown in the pressure-temperature phase diagram in Figure 1.

[0019] Therefore, the inventors have developed a method for producing ammonia (NH 3 ) into a solid cubic crystal (cubic-(NH 3 We have been studying the medium to trap the oxygen in the borate glass matrix (B 2 O 3 -B(OH) 3 ) was conceived. 2 O 3 -B(OH) 3 ) is boron trioxide (B 2 O 3 It is produced by dehydrating an aqueous solution of boron trioxide (B2 O 3 When an aqueous solution of boron trioxide (B 2 O 3 ) component and orthoboric acid component (B(OH) 3 ) as the base structure of the glass matrix. This borate glass matrix is ​​called B 2 O 3 (gl)-B(OH) 3 It is written as (gl).

[0020] In this solution, ammonia (NH 3 ) is a cubic (cubic-(NH 3 )(cr)) and the borate glass matrix (B 2 O 3 -B(OH) 3 )(gl)), it is possible for it to exist stably in a solid state at room temperature and pressure.

[0021] Solidified cubic ammonia (cubic-(NH 3 )(cr)) is a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) to form a core-shell structure. 3 )(cr)) and borate glass matrix (B 2 O 3 (gl)-B(OH) 3 At the interface of the solid ammonia cubic crystal (NH 3 )(cr)) standard Gibbs energy of formation (Δ f G ° m ) and the Gibbs energy of this interface (Δ boundary G ° m ) is the sum of gaseous ammonia (NH 3 (g)) Gibbs energy (Δ f G °m ) and ammonia (NH 3 ) maintains a stable solid cubic crystal structure at room temperature and pressure.

[0022] Δ f G ° m (NH 3 (cr))+Δ boundary G ° m <Δ f G ° m (NH 3 (g)), T / K>298.15··(1)

[0023] The borate glass matrix of the present solution (B 2 O 3 (gl)-B(OH) 3 (gl)) contains solid cubic ammonia (cubic-(NH 3 )(cr)) is trapped in hydrogen storage fuel, which is ammonia (NH 3 ) dissolved in an aqueous solution of boric acid (B 3 O 2 ) can be mixed and freeze-dried to prepare a mixed aqueous solution.

[0024] Here, ammonia (NH 3 ) is the ammonium ion (NH 4 + When this mixed aqueous solution is frozen and solidified using liquid nitrogen as a refrigerant, ammonia (NH 3 ) is the water component (H 2 O) freezes into a solid (ice) (H 2 0(cr)) matrix, solid ammonium ions (NH 4 + At low temperatures, when the mixed aqueous solution is frozen, the ammonium ions (NH 4 + (cr)) is ammonia gas (NH 3 (g)), due to the requirement of electrical neutrality, ice (H 2Hydroxide ions (OH O(cr)) - However, when the mixed solution is frozen at low temperatures, the hydroxide ions (OH - (cr)) cannot move. As a result, the solid ammonium ion (NH 4 + (cr)) does not sublime but is concentrated.

[0025] The frozen solidified mixture of the aqueous solution is then dried in a vacuum-suctioned reduced pressure atmosphere. During the drying process, the sublimated water vapor (H 2 O(g)) and boric acid (B 3 O 2 ) to evacuate all boron compounds (BHO(g)) derived from the Water vapor (H 2 When all the O(g) and boron compounds (BHO(g)) are pumped out, solid ammonium ions (NH 4 + As shown in the schematic diagram of Figure 2, the borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) contains cubic ammonia (NH 3 (cr)) is trapped.

[0026] In addition, the borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) is a solid product at room temperature and pressure.

[0027] Through the above-mentioned treatment process, ammonia (NH 3 ) as a solid cubic crystal in a borate glass matrix (B 2 O 3 -B(OH) 3 This product constitutes a hydrogen storage fuel that carries hydrogen in the form of ammonium.

[0028] By the way, ammonia (NH 3 ) dissolved in an aqueous solution of boric acid (B 3 O 2 When the mixed aqueous solution containing ammonium pentaborate and ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 ) and ammonia borane (NH 3 BH 3 ) is mixed into the fuel and solidified. Therefore, the hydrogen storage fuel produced by freeze-drying this mixed aqueous solution contains ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 ) and ammonia borane (NH 3 BH 3 ) is mixed in. Effect of the Invention

[0029] The hydrogen storage fuel according to the present invention is hydrogen (H 2 ) as a reservoir for ammonia (NH 3 ) in a stable solid state at room temperature and pressure, in a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 By confining it in (gl), it can be stored safely and can be easily transported.

[0030] Solid ammonia (NH 3 ) can be used as a hydrogen storage fuel and as a hydrogen energy carrier that can be widely and generally used, and is useful as fuel for ammonia engine systems, ammonia power generation systems, and other ammonia-fueled equipment. [Brief description of the drawings]

[0031] [Figure 1] The pressure-temperature phase diagram for ammonia (NH3) is shown below. [Diagram 2]This is a schematic diagram showing a core-shell structure in which ammonia (NH3) is trapped as solid cubic ammonia crystals (NH3(cr)) in a borate glass matrix (B2O3(gl)-B(OH)3(gl)). [Diagram 3] 1 is a schematic diagram showing a production apparatus used for producing hydrogen storage fuel according to the present invention. [Figure 4] This is a photograph showing the appearance of hydrogen storage fuel, which is a solidified solution obtained by freeze-drying a mixed solution of an aqueous solution of ammonia (NH3) and boric acid (B3O2). [Diagram 5] FIG. 2 is a diagram showing an X-ray diffraction (XRD) pattern of the hydrogen storage fuel according to the present invention. [Figure 6] FIG. 1 is a diagram showing the relationship between the diffraction angle (θ) of the peaks of the (111), (210) and (211) planes of ammonia cubic crystals (NH3(cr)) constituting the product produced by the method of the present invention and the lattice constant. [Figure 7] FIG. 2 shows a temperature-weight change diagram of the hydrogen storage fuel according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a hydrogen storage fuel and a method for producing the same according to the present embodiment will be described with reference to the drawings.

[0033] The hydrogen storage fuel according to the present embodiment is ammonia (NH 3 ) is a solid cubic crystal at room temperature and pressure, and is formed in a borate glass matrix (B 2 O 3 -B(OH) 3 (gl)) and is composed of the

[0034] By the way, ammonia (NH 3 As shown in the pressure-temperature phase diagram in Figure 1, the temperature (T) at the triple point is 195.5K and the pressure (p) is 0.0609 bar. 4 ) is converted into ammonia (NH3 ) is a solid cubic (NH 3 )(cr)). Therefore, ammonia (NH 3 ) cannot exist as a solid cubic crystal at room temperature and pressure, as shown in the diagram in Figure 1.

[0035] In this embodiment, ammonia (NH 3 ) is converted into a solid cubic crystal (cubic-(NH 3 )(cr)) as borate glass matrix (B 2 O 3 -B(OH) 3 (gl)) is a hydrogen storage fuel that can exist stably in a solid state at room temperature and pressure.

[0036] The hydrogen storage fuel according to the present embodiment is produced using a production apparatus shown in Fig. 3. As shown in Fig. 3, this production apparatus is a process for adding boric trioxide (B 2 O 3 (cr)) The system is equipped with a reaction vessel 1 into which a mixed aqueous solution containing powder is poured, a copper vacuum vessel 2 in which the reaction vessel 1 is housed, and a main cooling vessel 3 filled with liquid nitrogen. The vacuum vessel 2 is placed inside the main cooling vessel 3 which is filled with liquid nitrogen with a boiling point of 77.5K, and is cooled together with the reaction vessel 1 by the liquid nitrogen filled in the main cooling vessel 3.

[0037] The vacuum chamber 2 housing the reaction vessel 1 is connected to the outside of the main cooling chamber 3 via an exhaust valve 4. The exhaust valve 4 is attached to hermetically seal the main cooling chamber 3. This exhaust valve 4 opens and closes the vacuum chamber 2 by operating an opening and closing valve provided inside.

[0038] A vacuum pump 5 is connected to the vacuum chamber 2. A gas trap mechanism 6 is provided between the vacuum pump 5 and the vacuum chamber 2. This gas trap mechanism 6 is installed in an auxiliary cooling chamber 7 and is cooled by liquid nitrogen filled in the auxiliary cooling chamber 7. The vacuum chamber 2 and the gas trap mechanism 6 are connected via a connecting pipe 8. One end of this connecting pipe 8 is connected to the vacuum chamber 2 via an exhaust valve 4, and the other end passes through the auxiliary cooling chamber 7 and is inserted into the gas trap mechanism 6, thereby connecting the main cooling chamber 3 and the gas trap mechanism 6.

[0039] The vacuum pump 5 is connected to the gas trap mechanism 6 via a vacuum pump connecting pipe 9. One end of the vacuum pump connecting pipe 9 is connected to the vacuum pump 5, and the other end is inserted into the gas trap mechanism 6 through the auxiliary cooling tank 7, connecting the vacuum pump 5 and the exhaust gas trap mechanism 6.

[0040] Therefore, the inside of the vacuum chamber 2 is depressurized by suction with the vacuum pump 5 via the gas trap mechanism 6. Then, the gas sucked from the vacuum chamber 2 by driving the vacuum pump 5 is discharged to the outside of the vacuum chamber 2 via the exhaust valve 4, introduced into the gas trap mechanism 6 via the connecting pipe 8, and cooled by the liquid nitrogen filled in the auxiliary cooling tank 7.

[0041] A rubber cap 10 is provided on the top of the reaction vessel 1 placed in the vacuum chamber 2. A minute through hole 11 is formed in this cap 10. When the inside of the vacuum chamber 2 is evacuated, the reaction vessel 1 is evacuated through the through hole 11 in a state cooled by the liquid nitrogen filled in the main cooling chamber 3.

[0042] A process for producing the hydrogen storage fuel according to this embodiment using the production apparatus having the above-mentioned configuration will be described.

[0043] First, the starting material, ammonia (NH 3 ) and boric acid trioxide (B 2 O 3 (cr)) powder was prepared and dissolved in ammonia water.2 O 3 (cr) Prepare a mixed aqueous solution by mixing the powders.

[0044] In the present embodiment, a solid cubic ammonia (cubic-(NH 3 )(cr)) in a borate glass matrix (B 2 O 3 -B(OH) 3 In order to confine the cations in the core shell structure shown in FIG. 2, it is desirable to form sufficient BN bonds. Therefore, the mixed aqueous solution is prepared by dissolving ammonia (NH 3 ) aqueous solution (ammonia water) and boric acid (B 2 O 3 (cr)) is adjusted. In other words, the amount of boron and nitrogen is 4.6×10 -3 Adjust to make molar.

[0045] In this embodiment, the mixed aqueous solution contains ammonia (NH 3 ) was used, and boric acid trioxide (B 2 O 3 (cr)) powder was used. Ammonia water and boric acid trioxide (B 2 O 3 The boron (B) and nitrogen (N) powders are mixed in a mixed aqueous solution so that the ratio of boron (B) and nitrogen (N) in the mixed aqueous solution is 1:1. In this embodiment, the mixed aqueous solution is a mixture of 0.3 mL of ammonia water and 1.5 mL of boric acid (B 2 O 3 (cr)) It was made by mixing 160 mg of powder.

[0046] In addition, ammonia water and boric acid trioxide (B 2 O 3 (cr)) powder may be mixed in any suitable ratio so long as the ratio of boron (B) and nitrogen (N) in the mixed aqueous solution is approximately 1:1. For example, ammonia water is ammonia (NH 3 ) at a ratio of 20-30 wt%, and boric acid trioxide (B 2 O3 The (cr) powder may also have a purity in the range of 95 to 99.9%.

[0047] The mixed aqueous solution used in this embodiment is boric acid trioxide (B 2 O 3 (cr)) It is prepared by injecting ammonia water into a reaction vessel 1 containing powder.

[0048] The upper opening of the reaction vessel 1, which is filled with the mixed aqueous solution produced by injecting the ammonia water, is covered with a cap 10.

[0049] The reaction vessel 1 filled with the mixed aqueous solution is placed in the vacuum chamber 2 of the above-mentioned manufacturing equipment. The vacuum chamber 2 containing the reaction vessel 1 is placed in the main cooling chamber 3 filled with liquid nitrogen with a boiling point of 77.5K.

[0050] Next, liquid nitrogen is filled into the main cooling tank 3, and the vacuum tank 2 installed in the main cooling tank 3 and the reaction vessel 1 housed in the vacuum tank 2 are cooled. At this time, the mixed aqueous solution in the reaction vessel 1 contains at least ammonia (NH 3 The mixed aqueous solution is then cooled to -78°C or lower, at which point the aqueous solution solidifies, and the frozen solid is formed. The frozen solid state of the mixed aqueous solution in the reaction vessel 1 is then maintained for 1-2 hours.

[0051] Thereafter, the exhaust valve 4 provided on the vacuum chamber 2 is opened, and the vacuum pump 5 is driven to evacuate the inside of the vacuum chamber 2 and reduce the pressure. This evacuation is performed for an appropriate time within the range of 2 to 5 hours. When the vacuum chamber 2 is evacuated, the inside of the reaction vessel 1 is also evacuated through the through hole 11 provided in the cap 10 and reduced in pressure. As the reaction vessel 1 is evacuated, the mixed aqueous solution frozen and solidified in the reaction vessel 1 is freeze-dried.

[0052] When the frozen solidified material in the reaction vessel 1 is freeze-dried, the frozen solidified material sublimes and generates sublimation water vapor (H 2O(g)) is exhausted to the outside of the reaction vessel 1 through the through hole 11, and is then suctioned into the vacuum chamber 2 and exhausted to the outside of the vacuum chamber 2 through the exhaust valve 4. Then, sublimated water vapor (H 2 O(g)) is discharged, concentrating the ammonia component contained in the frozen solid.

[0053] In this embodiment, when the frozen solidified material in the reaction vessel 1 is freeze-dried, gaseous hydrogen nitride (NH(g)) and boron compounds (BHO(g)) are inevitably generated. These hydrogen nitride (NH(g)), boron compounds (BHO(g)) and sublimated water vapor (H 2 The hydrogen nitride (NH(g)), boron compound (BHO(g)), and sublimated water vapor (H2O(g)) introduced into the gas trap tank 6 are sucked in by the vacuum pump 5, exhausted to the outside of the vacuum tank 2 through the exhaust valve 4, and discharged to the outside of the vacuum tank 2 through the connecting pipe 8, and introduced into the gas trap mechanism 6. 2 O(g)) is cooled and frozen by liquid nitrogen filled in auxiliary cooling tank 7 in which gas trap tank 6 is installed, and is recovered as ammonia borate water.

[0054] That is, the gas trap mechanism 6 is cooled by liquid nitrogen, and the boron nitride (NH(g)), boron compound (BHO(g)), and sublimated water vapor (H 2 O(g)) is coagulated to produce ammonia water and boric acid water, and the mixed aqueous solution is taken out of the processing system where it is freeze-dried.

[0055] Then, after the above-mentioned process of freeze-drying the mixed aqueous solution filled in the reaction vessel 1 is appropriately performed within a range of 2 to 5 hours, the vacuum chamber 2 is taken out of the main cooling chamber 3 with the reaction vessel 1 stored therein and is recovered. The vacuum chamber 2 is subjected to a sudden change in temperature when it is taken out of the main cooling chamber 3. The sudden change in temperature of the vacuum chamber 2 may cause condensation inside, and the frozen solidified material in the reaction vessel 1 may absorb moisture.

[0056] Therefore, in this embodiment, the vacuum chamber 2 is removed from the main cooling chamber 3 with the exhaust valve 4 closed and the inside of the vacuum chamber 2 evacuated to a vacuum. The vacuum chamber 2 is then maintained in an evacuated state for a period of time until the inside of the reaction vessel 1 housed therein reaches room temperature sufficiently. In this embodiment, the vacuum chamber 2 is maintained in an evacuated state for at least 2-3 hours, thereby preventing a sudden change in temperature and suppressing the occurrence of condensation. By suppressing condensation in the vacuum chamber 2, the frozen solidified material in the reaction vessel 1 is prevented from becoming wet, and the freeze-dried state can be maintained.

[0057] Then, when the temperature inside the vacuum chamber 2 has sufficiently reached room temperature, the reaction vessel 1 is removed from the reaction vessel 2. The product of the mixed aqueous solution freeze-dried in the reaction vessel 1 is collected as a powdery solid.

[0058] The starting material for the solidified body produced in this embodiment is ammonia water, to which boric acid trioxide (B 2 O 3 When the mixed aqueous solution containing ammonia and cubic ammonia (NH(cr)) is freeze-dried, the ammonia water turns into solid ammonia cubic crystals (cubic-(NH 3 )(cr)) is produced, and boron trioxide (B 2 O 3 (cr)) to B 2 O 3 component and orthoboric acid component (B(OH) 3 ) consisting of a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) is generated.

[0059] The mixed aqueous solution was then freeze-dried to produce a solid ammonia cubic crystal (cubic-(NH 3 )(cr)) and borate glass matrix (B 2 O 3 (gl)-B(OH) 3 In the solidified body consisting of the above-mentioned SiO2 and SiO2, N atoms and B atoms are strongly bonded to generate boron nitride (BN), and the borate glass matrix (B 2 O 3 (gl)-B(OH)3 (gl)) forms a strong BN bond at the glass interface.

[0060] As a result, as mentioned above, cubic ammonia (cubic-(NH 3 )(cr)) standard Gibbs energy of formation (Δ f G ° m ) and a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) interface Gibbs energy (Δ boundary G ° m ) is the sum of gaseous ammonia (NH 3 (g)) standard Gibbs energy of formation (Δ f G ° m ) is more negative than that of the cubic ammonia (cubic-(NH 3 )(cr)) is a stable solid with a cubic crystal structure at room temperature and pressure.

[0061] Therefore, the ammonia (NH 3 ) dissolved in an aqueous solution of boric acid (B 3 O 2 The solidified material produced by freeze-drying the mixed aqueous solution of ammonia (NH 3 ) was solidified as a cubic crystal at room temperature and pressure, and the borate glass matrix (B 2 O 3 -B(OH) 3 (gl)). This solidified body constitutes a hydrogen storage fuel with solid ammonia as a water storage medium. This hydrogen storage fuel is used as fuel for ammonia engine systems, ammonia power generation systems, and other ammonia fuel devices. EXAMPLES

[0062] Next, an embodiment of the hydrogen storage fuel according to the present invention will be described. The embodiment shown below uses ammonia (NH 3) is shown as an example of a hydrogen storage fuel in a solid state, and the present invention is not limited to this example.

[0063] In this example, ammonia (NH 3 ) and boric acid trioxide (B 2 O 3 (cr)) powder was prepared and dissolved in ammonia water to obtain boric acid trioxide (B 2 O 3 The mixed aqueous solution was prepared by mixing boric acid trioxide (B(cr)) powder in a reaction vessel 1 used in the manufacturing apparatus shown in FIG. 2 O 3 (cr)) Powder is added and then ammonia water is injected.

[0064] Here, ammonia water and boric acid trioxide (B 2 O 3 The (cr)) powders were mixed so that the ratio of boron (B) and nitrogen (N) in the mixed aqueous solution was 1:1. That is, the mixed aqueous solution of this example had a substance amount of boron (B) and nitrogen (N) of 4.6 × 10 -3 Boric acid (B) was added to 0.3 mL of ammonia water to obtain 1.5 moles. 2 O 3 (cr)) 160 mg of powder was mixed together to prepare the sample.

[0065] Then, the reaction vessel 1 filled with the mixed aqueous solution has a cap 10 placed on the upper opening, and is stored and placed in a vacuum chamber 2 of a manufacturing device. The vacuum chamber 2 in which the reaction vessel 1 is placed is placed in a main cooling chamber 3 filled with liquid nitrogen. At this time, the vacuum chamber 2 is placed in a sealed state with the exhaust valve 4 closed. Next, the main cooling tank 3 is filled with liquid nitrogen with a boiling point of 77.5 K, and the vacuum tank 2 and the reaction vessel 1 placed in the vacuum tank 2 are cooled. At this time, the mixed aqueous solution in the vacuum tank 2 contains at least ammonia (NH 3 The mixed aqueous solution was then cooled to below 195.5K at which the aqueous solution solidified, and the frozen solid was formed. The frozen and solidified state of the mixed aqueous solution in the reaction vessel 1 was then maintained for one hour.

[0066] Thereafter, the exhaust valve 4 provided on the vacuum chamber 2 is opened, and the vacuum pump 5 is driven to evacuate and reduce the pressure inside the vacuum chamber 2 for two hours. When the vacuum chamber 2 is evacuated, the inside of the reaction vessel 1 is also evacuated and reduced in pressure through the through hole 11 provided in the cap 10. By evacuating the reaction vessel 1, the frozen solid of the mixed aqueous solution frozen and solidified inside the reaction vessel 1 is freeze-dried.

[0067] When the frozen solidified material in the reaction vessel 1 is freeze-dried, the frozen solidified material sublimes and generates sublimation water vapor (H 2 O(g)) is exhausted to the outside of the reaction vessel 1 through the through hole 11, and is then vacuum-sucked into the reaction vessel 2 and exhausted to the outside of the reaction vessel 2 through the exhaust valve 4. Then, sublimated water vapor (H 2 O(g)) is discharged, concentrating the ammonia component contained in the frozen solid.

[0068] In this embodiment, when the frozen solid in the reaction vessel 1 is freeze-dried, gaseous hydrogen nitride (NH(g)) and boron compounds (BHO(g)) are inevitably generated. These hydrogen nitride (NH(g)), boron compounds (BHO(g)) and sublimated water vapor (H 2 The hydrogen nitride (NH(g)) and boron compound (BHO(g)) introduced into the gas trap tank 6, together with the sublimated water vapor (H 2 O(g)) is cooled and frozen by liquid nitrogen filled in auxiliary cooling tank 7 equipped with gas trap tank 6, and is recovered as ammonia boric acid water. The recovered ammonia boric acid water is taken out of the processing system where the mixed aqueous solution is freeze-dried.

[0069] After performing the above-mentioned freeze-drying process for the mixed aqueous solution filled in the reaction vessel 1 for 2 hours, the vacuum chamber 2 with the reaction vessel 1 stored therein is removed to the outside of the main cooling chamber 3 and recovered. At this time, the vacuum chamber 2 is removed from the main cooling chamber 3 with the exhaust valve 4 closed and the inside of the vacuum chamber 2 evacuated to a vacuum. The vacuum chamber 2 is maintained in an evacuated state for a period of time until the inside of the reaction vessel 1 stored therein reaches room temperature sufficiently. In this embodiment, the vacuum chamber 2 is maintained in an evacuated state for at least 2 hours, and the reaction vessel 1 stored in the vacuum chamber 2 is removed when the inside of the vacuum chamber 2 reaches room temperature sufficiently. The product of the mixed aqueous solution freeze-dried in the reaction vessel 1 is recovered as a white powdery solidified body, as shown in the photograph in FIG. 4. Commercially available ammonia water contains vaporized ammonia (NH 3 Although the solid ammonia (NH 3 The product, which was mainly composed of (cr), was odorless.

[0070] The product produced as a white powder solid was ground into a fine powder and identified by X-ray diffraction (XRD). The X-ray diffraction (XRD) pattern of this product at 297 K is shown in Figure 5 (a), which shows that the main product is solid ammonia (NH 3 That is, the X-ray diffraction (XRD) pattern of the product, which shows a main peak at 2θ of 30.00 deg, corresponds to the solid ammonia (NH 3 It matched the shape of (cr).

[0071] At atmospheric pressure (1 atm), ammonia (NH 3 (cr)) was confirmed to exist as a stable solid even at room temperature. Furthermore, the main product produced by this example was solid ammonia (NH 3 The lattice constant of (cr) was investigated.

[0072] First, solid ammonia (NH 3 (cr)) has a crystal structure of a well-established ammonia cubic crystal (NH 3 The lattice constant (a) was calculated from the peak diffraction angles (θ) of the (111), (210) and (211) planes of (cr) according to the following formula (2). Sin 2 θ=λ 2 / 4a 2 ·(h 2 +k 2 +l 2 ) ···(2)

[0073] Here, the wavelength of Kα radiation emitted from pure copper (Cu) used in the X-ray diffraction (XRD) method is 0.154056 nm. h, k, and l are plane indices. And, ammonia cubic (NH 3 The lattice constant was calculated by extrapolating the results obtained from the diffraction angles (θ) of the peaks of the (111), (210) and (211) planes of (cr) up to 90 degrees. That is, as shown in FIG. 6, the lattice constant obtained from each plane was multiplied by 1 / 2(cos 2 The lattice constant was determined by plotting the lattice constant against the angle (θ / sinθ+cos2θ / θ) and extrapolating to 90 degrees using the least squares method.

[0074] The main product produced in this example was solid cubic solid ammonia (NH 3 The lattice constants of solid cubic ammonia (NH(cr)) were determined by the in situ XRD method at 171K and 77K proposed by Olovson and Templeton. 3 The lattice constants of the Cr-based alloys were compared with those of the Cr-based alloys.

[0075] The solid cubic solid ammonia (NH 3 The lattice constant of (cr)) was 0.5165 nm, which agreed well with the lattice constants of 0.5138 nm and 0.5073 nm obtained by in situ XRD at 171 K and 77 K reported by Olovoson and Templeton.

[0076] The lattice constant in this example is 0.0027 nm larger than the lattice constant at 171 K shown by Olovoson and Templeton. This is believed to be due to the difference in thermal expansion.

[0077] Therefore, the solid ammonia cubic crystal (NH 3 The volume expansion coefficient (α) calculated from the difference between the lattice constant of (cr) and the lattice constant at 171K given by Olovoson and Templeton is 1.26×10 -4 On the other hand, the volume expansion coefficient calculated from the difference between the lattice constants at 171K and 77K, as shown by Olovoson and Templeton, was 3.32×10 -4 It was.

[0078] From the viewpoint of the thermal expansion coefficient, the solid ammonia cubic crystal (NH 3 (cr)) and 171K, and the thermal expansion coefficient (α) of solid ammonia (NH 3 A good correspondence was found between the thermal expansion coefficient (α) of (cr) and As described above, cubic solid ammonia (NH 3 As clarified by the verification from the viewpoint of the lattice constant and thermal expansion coefficient of ammonia (NH(cr)), the product produced by this example is a solid ammonia cubic crystal (NH 3 (cr)) as the main product.

[0079] In the product produced in this example, the X-ray diffraction (XRD) pattern at 297 K shows that the main product is solid cubic ammonia (NH 3 In addition to the peaks of ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 )(cr)), and ammonium borane (NH 3 BH 3These peaks correspond to boric acid (B 2 O 3 It is an unavoidable impurity phase derived from (cr).

[0080] Next, the main product of this example, solid cubic ammonia (NH 3 (cr)) to gaseous ammonia (NH 3 Explain the process by which (g)) is generated. The solid ammonia (NH 3 The XRD pattern of the product containing ammonia cubic crystals (NH3(cr)) when it was kept under an atmosphere of 363K for 4 hours is shown in FIG. 5(b). 3 (cr)) is converted into gaseous hydrogen (H 2 (g)) is eliminated.

[0081] NH 3 (cub)=3 / 2H 2 (g) + N(radical) · · · (3) Here, N (radical) is atomic nitrogen, which is unstable and therefore cannot be dissolved in a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) reacts immediately with the B, O, and H components to produce ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 (cr)).

[0082] As a result, as shown in FIG. 5(b), the remaining ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 ) peak was observed. That is, when the product of this example was produced, and when the ammonia cubic crystal (NH 3(cub)) from hydrogen (H 2 (g)) Ammonium pentaborate tetrahydrate (NH 4 B 5 O 8 (H 2 O) 4 ) peak was detected.

[0083] As a result, the solid ammonia cubic crystals (NH 3 (cr)) at low temperatures, i.e., with little energy consumption, to produce gaseous hydrogen (H 2 (g)) can be converted.

[0084] The solid ammonia cubic crystal (NH 3 The X-ray diffraction (XRD) pattern of the product containing ammonium pentaborate tetrahydrate ((NH 4 B 5 O 8 (H 2 O) 4 It was confirmed that the peaks of (cr) and (cr) disappeared. This is the result of the progress of the thermal decomposition shown in the following formula (4).

[0085] NH 4 B 5 O 8 4H 2 O)(cr) =NH 3 (g)+4H 2 O(g)+2B 2 O 3 (g) + BHO(g) + 1 / 2O 2 (4)

[0086] As a result, as shown in FIG. 5(c), the remaining glass matrix B 2 O 3 (gl)-B(OH) 3 Only a broad X-ray diffraction (XRD) pattern of (gl) was observed.3 (g)) is thermally decomposed to produce gaseous hydrogen (H 2 (g)) and nitrogen (N 2 (g)) and hydrogen (H 2 (g)) can be recovered.

[0087] As a result, the product produced by this example is solid cubic ammonia (NH 3 (cr)) and borate glass matrix B 2 O 3 (gl)-B(OH) 3 As described above, this solidified body is made of boron nitride (BN) formed by the strong bonding of N atoms and B atoms, and a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 At the glass interface of the cubic ammonia (NH (gl)), a strong BN bond is formed. 3 )(cr)) standard Gibbs energy of formation (Δ f G ° m ) and a borate glass matrix (B 2 O 3 (gl)-B(OH) 3 (gl)) interface Gibbs energy (Δ boundary G ° m ) is the sum of gaseous ammonia (NH 3 (g)) standard Gibbs energy of formation (Δ f G ° m ) and has a more negative value than the cubic ammonia (cubic-(NH 3 )(cr)) maintains a cubic crystal form as a stable solid at room temperature and pressure.

[0088] Therefore, the ammonia (NH 3 ) dissolved in an aqueous solution of boric acid (B 3 O 2 The solidified material produced by freeze-drying the mixed aqueous solution of ammonia (NH 3) as a solid cubic crystal at room temperature and pressure, and in a borate glass matrix (B 2 O 3 -B(OH) 3 ) in a solid cubic ammonia (NH 3 The hydrogen storage fuel is composed of hydrogen carriers such as hydrogen carbide (Cr).

[0089] Next, the ammonia cubic crystal (NH 3 (cr)) and ammonia (NH 3 ) and ammonium pentaborate tetrahydrate ((NH 4 B 5 O 8 (H 2 O) 4 The thermal decomposition process of Cr(Cr) was investigated.

[0090] The solid ammonia cubic crystal (NH 3 As shown in the temperature-weight change diagram in Figure 7, the hydrogen storage fuel incorporating ammonia (cr) did not show any weight loss at 325K or less. This is because ammonia becomes solid ammonia cubic (NH 3 (cr)) as ammonia storage medium and borate glass matrix (B 2 O 3 -B(OH) 3 ) and is deemed to be due to the fact that the subject remains confined within the enclosure.

[0091] As shown in FIG. 7, the hydrogen storage fuel of this embodiment gradually lost weight when heated from 325 K to 363 K, and rapidly lost weight when heated from 363 K to 750 K. This is because the ammonia cubic crystal particles (NH 3 At 363 K to 750 K, hydrogen is released from ammonium pentaborate tetrahydrate ((NH 4 B 5 O 8 (H 2 O) 4This is believed to be due to the thermal decomposition of hydrogen (Cr). Hydrogen has the smallest atomic weight, and as a result, the loss of weight from 325K to 363K is gradual.

[0092] Here, boric acid trioxide (B 2 O 3 The mixed solution of ammonia cubic (NH 3 (cr)) is a borate glass matrix (B 2 O 3 -B(OH) 3 The chemical composition of the product trapped in the (gl) was measured. The composition ratio is shown below. N 6.1 mol%, H 47.8 mol%, B 11.9 mol%, O 34.2 mol% The composition ratio was as follows.

[0093] In this measurement, N and H were measured by the combustion thermal conductivity method, B was measured by the ICP method, and O was estimated as the balance of N, H, and B.

[0094] Next, the amount of ammonia cubic crystals (NH 3 (cr)), ammonium pentaborate (NH 4 B 5 O 8 (H 2 O) 4 )(cr)), and borate glass matrix (GM)(0.17B 2 O 3 , 0.83B(OH) 3 The mole percent and weight percent concentrations of each phase of (gl) are shown in Table 1 below. 3 (Cr) is 37 mol% or 11 mass%, NH 4 B 5 O 8 (H 2 O) 4 is 5 mol%, i.e. 24 mass%, GM(0.17B 2 O 3 , 0.83B(OH) 3(gl)) was 58 mol%, or 65 mass%. [Table 1]

[0095] Next, ammonia cubic (NH 3 The molar and weight percent concentrations of N and H in (cr) were 25 mol% and 82.2 mass% for N, and 75 mol% and 17.8 mass% for H, respectively.

[0096] The mixed aqueous solution was then transferred to the borate glass matrix (B 2 O 3 -B(OH) 3 Ammonia cubic crystals (NH 3 The weight percent concentrations of N and H in (cr) were 9 mass% for N and 2 mass% for H.

[0097] That is, 2 mass% of hydrogen in the sample is ammonia cubic (NH 3 (cr)) and the borate glass matrix (B 2 O 3 -B(OH) 3 (gl)) and is released as gaseous hydrogen. In the temperature-weight change diagram shown in Figure 7, the temperature at which 2 mass% of hydrogen is lost is found to be 358 K. Therefore, it was found that the analysis based on this composition analysis is in good agreement with the results of the temperature-weight change diagram shown in Figure 7.

[0098] Conventionally, gaseous ammonia (NH 3 (g)) is heated to a high temperature of 673K ​​and nitrogen gas (N 2 (g)) and hydrogen gas (H 2 (g)) and hydrogen gas (H 2A method of recovering hydrogen from solid ammonia cubic crystals (NH 3 (cr)) and hydrogen is safely stored in a borate glass matrix (B 2 O 3 -B(OH) 3 (gl)) is permeated, and gaseous hydrogen (H 2 (g)) can be separated from the hydrogen gas, thus significantly reducing the energy required to store and reseparate hydrogen.

[0099] Therefore, the hydrogen storage fuel of this embodiment is ammonia (NH 3 ) into solid cubic ammonia (NH 3 It is possible to store and preserve hydrogen as hydrogen (H2O3) by heating it at a temperature slightly higher than room temperature. 2 (g)) can be extracted. Furthermore, by heating at a higher temperature, ammonia (NH 3 (g)) can be extracted, which can be decomposed using an ammonia decomposition catalyst to produce hydrogen.

[0100] The hydrogen storage fuel according to this embodiment can be transported and stored as a solid product under normal temperature and pressure conditions. [Industrial Applicability]

[0101] The hydrogen storage fuel according to the present invention is used as fuel for an ammonia engine system, an ammonia power generation system, and other ammonia fuel devices. [Explanation of symbols]

[0102] 1 Reaction vessel 2 Vacuum chamber 3 Main cooling tank 4 Exhaust valve 5. Vacuum Pump 6 Gas trap mechanism 7 Auxiliary cooling tank

Claims

1. A solid hydrogen storage fuel, comprising: Ammonia (NH ３ ) is a solid cubic crystal at room pressure and temperature, and is formed in a borate glass matrix (B ２ O ３ -B(OH) ３ ) trapped inside A hydrogen storage fuel.

2. As an inevitable impurity, ammonium pentaborate tetrahydrate (NH ４ B ５ O ８ (H ２ O) ４ ) and ammonia borane (NH ３ BH ３ ) is mixed in.

2. The hydrogen storage fuel according to claim 1.

3. Ammonia (NH ３ ) was dissolved in an aqueous solution of boric acid (B ３ O ２ ) to prepare a mixed aqueous solution, Next, the mixed aqueous solution is frozen to prepare a frozen solid, Thereafter, the frozen solid is freeze-dried to remove water vapor (H ２ O) and boron compounds (BHO) contained as gas are discharged, and ammonia (NH ３ ) is concentrated, The ammonia (NH ３ ) in a borate glass matrix (B ２ O ３ -B(OH) ３ ) as a solid cubic crystal at room temperature and pressure. A method for producing hydrogen storage fuel.

4. The ammonia (NH ３ ) is an inevitable impurity, ammonium pentaborate tetrahydrate (NH ４ B ５ O ８ (H ２ O) ４ ) and ammonia borane (NH ３ BH ３ ) together with the borate glass matrix (B ２ O ３ -B(OH) ３ ) and solidified. The method for producing hydrogen storage fuel according to claim 3.

5. 5. The method for producing a hydrogen storage fuel according to claim 3, wherein the mixed aqueous solution is cooled with liquid nitrogen to be frozen and solidified.

6. The method for producing hydrogen storage fuel according to any one of claims 3 to 5, characterized in that the frozen solid is subjected to a decompression treatment and freeze-dried while being cooled by liquid nitrogen.

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