Hydrogen production method

Abstract

The present invention relates to a hydrogen generation method including generation of hydrogen by a dehydrogenation reaction of a solid-state chemical hydride with an acidic aqueous solution. The dehydrogenation reaction is performed by reacting hydrogen atoms of 1 mole of the chemical hydride with an acid and water in a molar ratio of 0.5 to 2.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2021-0017385, filed with the Korean Intellectual Property Office on February 8, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to a method for generating hydrogen for supplying hydrogen to a fuel cell stack. Background Technology

[0004] Due to the depletion of fossil fuels and environmental pollution, the demand for renewable and alternative energy sources is increasing, and hydrogen is gaining attention as one such alternative energy source.

[0005] Fuel cells and hydrogen combustion devices use hydrogen as a reactant gas, and a stable and continuous hydrogen supply technology is required, for example, in order to apply fuel cells and hydrogen combustion devices to vehicles and various electronic products.

[0006] To supply hydrogen to devices that use hydrogen, a method can be used to receive hydrogen from a separately installed hydrogen supply source. In this way, either compressed hydrogen or liquefied hydrogen can be used.

[0007] An alternative method is to generate hydrogen through a reaction of the hydrogen storage material after it is installed in the hydrogen-using device, and then supply the hydrogen to the device. For this method, it is recommended to use chemical hydrogen storage materials, including liquid hydrides or solid hydrides.

[0008] On the other hand, sodium borohydride (NaBH4) is a solid hydrogen storage material that, in a hydrolysis reaction with 2 moles of water, can produce approximately 10.9 wt% of high-density hydrogen gas based on the material (based on 1 mole of sodium borohydride). However, in hydrolysis reactions using existing heterogeneous catalysts (platinum (Pt), nickel (Ni), cobalt (Co), etc.), conditions exist requiring the inclusion of 80 wt% or more of water to ensure reaction continuity. In this case, the hydrogen storage capacity relative to the material can be 2 wt% to 3 wt% or higher, but this is significantly lower than the inherent storage capacity of sodium borohydride.

[0009] Simultaneously, acids can be used as catalysts in the hydrolysis reaction of sodium borohydride, replacing solid, heterogeneous catalysts. However, this reaction is strongly exothermic, so water evaporates easily with increasing temperature, leading to decreased reactivity. To prevent this, an excess of water is required. Furthermore, when using strong acids (hydrogen chloride (HCl), sulfuric acid (H₂SO₄), nitric acid (HNO₃), etc.) to produce hydrogen gas, there is a high risk of metal corrosion, which can pose safety concerns. To prevent this, additional corrosion-resistant coatings for acid-containing containers may be required, and large quantities of water must be used for dilution to ensure acid safety.

[0010] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include information that does not constitute prior art known to those skilled in the art in this country. Summary of the Invention

[0011] The implementation provides a method for generating hydrogen while preventing water evaporation and reducing water consumption by reacting under high temperature and high pressure conditions, thereby maximizing the hydrogen generation capacity relative to the weight of materials and reducing the possibility of corrosion of the reaction device to improve the safety of the dehydrogenation reaction system.

[0012] According to an embodiment, a method for generating hydrogen is provided, the method comprising generating hydrogen through a dehydrogenation reaction of a solid chemical hydride with an acidic aqueous solution. The dehydrogenation reaction can be carried out by reacting 1 mole of hydrogen atoms of the chemical hydride with an acid and water in a molar ratio of 0.5 to 2.

[0013] Chemical hydrides may include sodium borohydride (NaBH4), lithium borohydride (LiBH4), potassium borohydride (KBH4), ammonium borohydride (NH4BH4), boraneammonium (NH3BH3), tetramethylammonium borohydride ((CH3)4NH4BH4), sodium aluminum hydride (NaAlH4), lithium aluminum hydride (LiAlH4), potassium aluminum hydride (KAlH4), calcium borohydride (Ca(BH4)2), magnesium borohydride (Mg(BH4)2), sodium gallium hydride (NaGaH4), lithium gallium hydride (LiGaH4), potassium gallium hydride (KGaH4), lithium hydride (LiH), calcium hydride (CaH2), magnesium hydride (MgH2), or mixtures thereof.

[0014] Acids may include sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, boric acid, heteropoly acids, acetic acid, formic acid, malic acid, citric acid, tartaric acid, ascorbic acid, lactic acid, oxalic acid, succinic acid, taurine, or mixtures thereof.

[0015] The temperature for the dehydrogenation reaction can range from 10°C to 400°C, and the pressure can range from 1 bar to 100 bar.

[0016] The dehydrogenation reaction can be carried out in the presence of a homogeneous catalyst, which includes ruthenium acetylacetonate (III) (Ru(acac)3), carbonyl chloride hydride {bis[2-(diphenylphosphinomethyl)ethyl]amino}ruthenium (II), ruthenium triphenylphosphine monosulfonate (II) (RuCl2(m-triphenylphosphine monosulfonate)2), benzene ruthenium (II), RuCl2 (benzene) having 1,2-bis(diphenylphosphino)methane, or combinations thereof.

[0017] The gaseous products produced in the dehydrogenation reaction may contain 99% or more hydrogen and 1% or less water.

[0018] The dehydrogenation reaction can be carried out in a dehydrogenation reactor apparatus, which includes a dehydrogenation reactor and an acidic aqueous solution tank. The dehydrogenation reactor contains a solid chemical hydride, and the acidic aqueous solution tank supplies the acidic aqueous solution to the dehydrogenation reactor. The dehydrogenation reactor may include heating devices, cooling equipment, porous foamed metal, or combinations thereof.

[0019] Porous foam metal can be porous foam nickel or porous foam cobalt-nickel.

[0020] Acidic aqueous solutions can be supplied to the dehydrogenation reactor by gravity or a pump.

[0021] The hydrogen generation method according to the implementation scheme can prevent water evaporation and reduce water consumption by reacting under high temperature and high pressure conditions, thereby maximizing the hydrogen generation capacity relative to the weight of the material. The hydrogen generation method can also improve system safety by reducing the risk of corrosion of the reaction apparatus. Furthermore, by using a homogeneous catalyst, additional hydrogen can be generated from the material after the hydrolysis reaction of the chemical hydride with acid. Attached Figure Description

[0022] Figure 1 A view schematically showing the dehydrogenation reaction apparatus.

[0023] Figure 2 for Figure 1 An enlarged cross-sectional view of the dehydrogenation reactor in the image.

[0024] Figure 3 A schematic view of a dehydrogenation reaction system connected to a fuel cell.

[0025] Figure 4 A graph showing the measurement results of the hydrogen storage capacity of the dehydrogenation reaction in Implementation Scheme 1.

[0026] Figure 5 A graph showing the measurement results of the hydrogen storage capacity of the dehydrogenation reaction in Implementation Scheme 2.

[0027] Figure 6A graph showing the measurement results of the hydrogen storage capacity of the dehydrogenation reaction in Implementation Scheme 3.

[0028] Figure 7 A graph showing the measurement results of the hydrogen storage capacity of the dehydrogenation reaction in Implementation Scheme 4.

[0029] Figure 8 A graph showing the measurement results of the hydrogen storage capacity of the dehydrogenation reaction in Implementation Scheme 5.

[0030] Figure 9 A graph showing the measurement results of the hydrogen conversion rate of the dehydrogenation reaction in Implementation Scheme 6.

[0031] Figure 10 A graph showing the measurement results of the hydrogen conversion rate of the dehydrogenation reaction in Implementation Scheme 7. Detailed Implementation

[0032] The advantages, features, and aspects described below will become apparent from the following description of embodiments with reference to the accompanying drawings. However, this application is not limited to the embodiments described herein. Although not specifically limited, all terms used herein, including technical and scientific terms, have the meaning understood by one of those skilled in the art. These terms have specific meanings and vocabulary meanings consistent with the relevant technical references and this specification. In other words, these terms should not be construed as having idealized or overly formal meanings. In the following specification and claims, unless expressly stated otherwise, variations of the terms “comprise / include” or, for example, “comprises / includes” or “comprising / including” should be understood to mean including the stated elements but not excluding any other elements.

[0033] Unless otherwise stated, a singular term may include a plural term.

[0034] In the accompanying drawings, the thickness of layers, films, sheets, areas, etc., is exaggerated for clarity. Throughout the specification, the same reference numerals denote the same elements.

[0035] The hydrogen generation method according to the implementation plan generates hydrogen through a dehydrogenation reaction between a solid chemical hydride and an acidic aqueous solution.

[0036] Solid chemical hydride 111 can be in any form, such as powder, granules, beads, microcapsules, or pellets. When chemical hydride 111 is stored in aqueous solution (in one embodiment, at a concentration of about 20% by weight of chemical hydride), large quantities of chemical hydride 111 cannot be stored, but when chemical hydride 111 is stored in solid form, large-capacity storage can be achieved.

[0037] Chemical hydrides can be any compound that can be hydrolyzed to produce hydrogen gas and hydrolysis products, for example, they can include NaBH4, LiBH4, KBH4, NH4BH4, NH3BH3, (CH3)4NH4BH4, NaAlH4, LiAlH4, KAlH4, Ca(BH4)2, Mg(BH4)2, NaGaH4, LiGaH4, KGaH4, LiH, CaH2, MgH2 or mixtures thereof.

[0038] Acidic aqueous solutions shorten the half-life of chemical hydride 111 by adjusting its pH, thereby promoting the dehydrogenation reaction.

[0039] The acid can be an inorganic acid (e.g., sulfuric acid, nitric acid, phosphoric acid, boric acid, or hydrochloric acid), an organic acid (e.g., heteropoly acids, acetic acid, formic acid, malic acid, citric acid, tartaric acid, ascorbic acid, lactic acid, oxalic acid, succinic acid, and taurine), or a mixture thereof. Due to its smaller molecular weight compared to hydrogen ions, the system weight can be reduced, and formic acid (HCOOH) can be used because it is safer than hydrochloric acid at high concentrations. In the case of formic acid (which is a weak acid), in one embodiment, under the conditions described in this application, the pH is maintained at approximately 2, thus formic acid can be used relatively safely. Furthermore, captured carbon dioxide can be obtained through hydrogenation, making it an important material for carbon dioxide recovery / recycling. Additionally, formate salts are converted to bicarbonates via dehydrogenation, allowing for the acquisition of additional hydrogen through hydrolysis.

[0040] For example, when Figure 2 and Figure 3 When the chemical hydride 111 is NaBH4 and the acid is HCOOH, the dehydrogenation reaction proceeds as shown in the following reaction formula 1. Sodium borohydride hydrolyzes to produce hydrogen gas and hydrolysis products. The acidic aqueous solution promotes the dehydrogenation reaction by supplying water as a reactant and protons as a catalyst for the reaction in which sodium borohydride produces hydrogen gas.

[0041] [Reaction Formula 1]

[0042] NaBH4+HCOOH+4H2O→HCOONa+H3BO3+H2O+4H2→HCO3Na+ H3BO3+5H2

[0043] In this way, when formic acid (HCOOH, which is a weak acid) is used as the acid, the safety of the system can be improved by preventing equipment corrosion, while increasing the amount of hydrogen produced.

[0044] Dehydrogenation can be achieved by reacting 1 mole of hydrogen atoms from a chemical hydride with an acid and water in a molar ratio of 0.5 to 2 in chemical hydride 111, thereby producing 4 moles or more of hydrogen gas. If the molar ratio of acid to water is less than 0.5, chemical hydride 111 may not react sufficiently, and if it is greater than 2, the system weight and reactor volume may increase.

[0045] On the other hand, when hydrogen is produced using acid and water through a hydrogen generation method, the water is prone to evaporation (water evaporation temperature: 100°C at 1 bar) because it is an exothermic reaction, and the amount of hydrogen produced (i.e., hydrogen storage capacity) may be reduced.

[0046] Therefore, the dehydrogenation reaction can be carried out under high temperature and high pressure conditions. This prevents water evaporation and reduces the amount of water used, thereby maximizing the amount of hydrogen produced (water evaporation temperature: 175°C at 10 bar, 260°C at 50 bar). Furthermore, CO2 production can be suppressed by pressurizing the reaction.

[0047] Furthermore, if the hydrogen gas contains excess water after the reaction, a separate gas-liquid separator can be used, which may increase the overall system volume and weight, and potentially reduce the hydrogen storage capacity. However, high-temperature, high-pressure reactions can prevent water evaporation, thereby increasing the hydrogen storage capacity and reducing system cost and weight.

[0048] For example, the temperature of a dehydrogenation reaction can range from 10°C to 400°C, or from 10°C to 250°C. If the temperature of the dehydrogenation reaction is below 10°C, the reaction rate may be low, and if it is above 400°C, byproducts (such as carbon dioxide and carbon monoxide) may be formed due to the decomposition of the products.

[0049] The pressure for the dehydrogenation reaction can range from 1 bar to 100 bar, or from 5 bar to 50 bar. If the pressure is less than 1 bar, the hydrolysis reaction is inhibited due to the evaporation of water at 100°C, resulting in a decrease in hydrogen storage capacity. If the pressure is greater than 100 bar, the cost of components and materials used to maintain the high pressure may increase.

[0050] Therefore, the gaseous products produced in the dehydrogenation reactor may contain 99% or more hydrogen, 1% or less water, and 0.1% or less other impurities.

[0051] The dehydrogenation reaction can be carried out in the presence of a ruthenium-based homogeneous catalyst to produce additional hydrogen. For example, the ruthenium-based homogeneous catalyst may include ruthenium(III) acetylacetonate (Ru(acac)3), carbonyl chloride hydrogen {bis[2-(diphenylphosphinemethyl)ethyl]amino}ruthenium(II), RuCl2 (m-triphenylphosphine monosulfonate)2, benzeneruthenium(II), RuCl2 (benzene) having 1,2-bis(diphenylphosphine)methane, or combinations thereof.

[0052] Meanwhile, the dehydrogenation reaction can be carried out in a dehydrogenation reaction device, which includes a dehydrogenation reactor and an acidic aqueous solution tank. The dehydrogenation reactor contains a solid chemical hydride, and the acidic aqueous solution tank supplies acidic aqueous solution to the dehydrogenation reactor.

[0053] Figure 1 To schematically show a view of the dehydrogenation reaction unit, Figure 2 for Figure 1 An enlarged cross-sectional view of the dehydrogenation reactor in [the image / project]. References are now available. Figure 1 and Figure 2 Describe the dehydrogenation reaction apparatus in detail.

[0054] refer to Figure 1 The dehydrogenation reaction apparatus 100 includes a dehydrogenation reactor 110 and an acidic aqueous solution tank 120.

[0055] The dehydrogenation reactor 110 may be composed of a high-temperature and high-pressure vessel, enabling the dehydrogenation reaction to be carried out under high-temperature and high-pressure conditions. For example, the dehydrogenation reactor 110 may have a shape such as a cylinder, sphere, cuboid, or polygonal prism, and in a particular embodiment, it may have a cylindrical shape.

[0056] refer to Figure 2 The dehydrogenation reactor 110 can have a high aspect ratio, where the ratio of length L to width D, L / D, is high. Here, the width D of the dehydrogenation reactor 110 is smaller than its length L.

[0057] In the dehydrogenation reactor 110, the length-to-width ratio L / D can be from 1 to 10. When the dehydrogenation reactor 110 has a high length-to-width ratio, the heat of reaction can be released to the maximum extent during the dehydrogenation reaction, and the pumps can be used as little as possible by utilizing the water level difference.

[0058] The dehydrogenation reactor 110 contains a solid chemical hydride 111.

[0059] The dehydrogenation reactor 110 is cylindrical, allowing for easy replacement. The upper part is designed to be openable or closed, enabling the injection or replacement of chemical hydride 111, or allowing product discharge through the lower part while chemical hydride 111 can be injected, thus ensuring system continuity of the dehydrogenation reactor 110. Furthermore, the dehydrogenation reactor 110 may also include sections for discharging slurry-like hydrolysis reaction products and sections for injecting chemical hydride 111.

[0060] The dehydrogenation reactor 110 may include a heating device that provides heat / temperature for the hydrolysis of chemical hydrides 111 or for other purposes, a cooling device 230 that removes the heat of reaction H when the reaction that produces hydrogen is exothermic, or a porous foam metal 112 that improves heat transfer and increases the reaction rate through catalytic reaction.

[0061] For example, the heating device can use electricity or other heat sources, and the cooling device 230 can be implemented as a refrigerant circulation device to dissipate the heat generated by the hydrolysis of chemical hydride 111.

[0062] The porous foam metal 112 has a honeycomb structure, consisting of a solid metal with inflatable pores of a predetermined volume. The pores can be sealed (closed-cell recesses) or interconnected (open-cell foam), and the porous foam metal 112 can be an open-cell recess. The porous foam metal 112 can have high porosity; for example, only 5% to 25% of the total volume can be metal. Therefore, the porous foam metal 112 can be ultralight while having a high profile area. Furthermore, the porous foam metal 112 can have various characteristics, such as porosity, pore volume, thickness, alloy composition, or density. The porous foam metal 112 can be formed integrally or arranged by stacking at least one or more porous foam metals.

[0063] Considering the increased reaction rate through catalysis and heat conduction, various materials can be used for the porous foam metal 112. For example, the porous foam metal 112 can be porous nickel foam or porous cobalt-nickel foam. Using porous nickel foam or porous cobalt-nickel foam can be advantageous because it can serve as a homogeneous catalyst to accelerate the hydrolysis of chemical hydrides. In the case of using porous nickel foam or porous cobalt-nickel foam, heat transfer can be accelerated, and the reaction can be accelerated through the catalytic action of the metal. It can also help release the heat of reaction inside the dehydrogenation reactor 110. Furthermore, it can act as a distributor, allowing the acidic aqueous solution to be uniformly supplied to the dehydrogenation reactor 110.

[0064] The porous foam metal 112 is located at the center of the dehydrogenation reactor 110 in the width direction and extends in the length direction of the dehydrogenation reactor 110. At this time, the chemical hydride 111 can be located on the outside of the dehydrogenation reactor 110 in the width direction, and the side of the porous foam metal 112 in the length direction can be surrounded by the chemical hydride 111.

[0065] Furthermore, the porous foam metal 112 can be connected to the inlet side through which the acidic aqueous solution supplied from the acidic aqueous solution tank 120 flows in. In this case, the opposing surfaces of the porous foam metal 112 and the surface connected to the dehydrogenation reactor 110 can be surrounded by chemical hydride 111.

[0066] Porous foam metal 112 can uniformly distribute acidic aqueous solutions to chemical hydride 111, thereby maximizing heat transfer and serving as a heterogeneous catalyst for the dehydrogenation reaction. Therefore, barriers formed by byproducts (e.g., borates) generated by chemical hydride 111 after the dehydrogenation reaction can be suppressed, and reaction delay can be minimized, thereby maximizing hydrogen production.

[0067] The dehydrogenation reactor 110 may contain 0 to 100 parts by volume of porous foam metal 112 relative to 100 parts by volume of chemical hydride 111, for example, it may contain 0 to 50 parts by volume of porous foam metal 112. If more than 50 parts by volume of porous foam metal 112 are contained per 100 parts by volume of chemical hydride 111, the hydrogen storage capacity may be reduced due to space constraints.

[0068] Acidic aqueous solution tank 120 supplies acidic aqueous solution to dehydrogenation reactor 110. In other words, dehydrogenation reactor 100 is a system that produces hydrogen by injecting acidic aqueous solution into dehydrogenation reactor 110 containing solid chemical hydride 111.

[0069] Furthermore, since a separate recovery tank can be omitted in some cases, the cost and weight of the system can be reduced. In particular, when the product is present in the container as a highly fluid slurry, it is advantageous that the product can be easily discharged under pressure conditions above 100°C and above atmospheric pressure.

[0070] The acidic aqueous solution tank 120 may have a corrosion-resistant protective film (such as a Teflon coating) to prevent corrosion from the acidic aqueous solution.

[0071] The acidic aqueous solution tank 120 is positioned above the dehydrogenation reactor 110 relative to the direction of gravity, and can supply acidic aqueous solution to the dehydrogenation reactor 110 via gravity or a high-pressure pump. In other words, the acidic aqueous solution tank 120 can supply acidic aqueous solution to the dehydrogenation reactor 110 due to the water level difference. In this way, system cost and weight can be reduced by using as few pumps as possible. However, this application is not limited to this; the acidic aqueous solution tank 120 can also be positioned below the dehydrogenation reactor 110 in the direction of gravity, and the acidic aqueous solution can be supplied to the dehydrogenation reactor 110 via a high-pressure pump. In other words, when the acidic aqueous solution is injected into the dehydrogenation reactor 110 via a high-pressure pump, the pressure of the acidic aqueous solution tank can be ignored, and in this case, there is no positional limitation.

[0072] For this purpose, the acidic aqueous solution tank 120 can have the same pressure as or higher than that of the dehydrogenation reactor 110, and a valve 710, such as a solenoid valve, can be installed between the acidic aqueous solution tank 120 and the dehydrogenation reactor 110. In this case, the acidic aqueous solution tank 120 does not need to be located above the dehydrogenation reactor 110, and can be located at the same or lower position as the dehydrogenation reactor 110. For example, the acidic aqueous solution tank 120 can be pressurized using hydrogen gas generated in the dehydrogenation reactor 110. In addition to using the above method, an acidic aqueous solution at atmospheric pressure can also be injected into the dehydrogenation reactor 110 using a high-pressure pump.

[0073] The rate of hydrogen production in the dehydrogenation reactor 110 can be controlled by altering the injection rate of the acidic aqueous solution or by changing the injection time (valve opening time) while maintaining a constant injection rate. Therefore, since a separate pump is not required, the system cost and weight can be reduced.

[0074] Hydrogen generation reactions can be carried out in dehydrogenation reaction systems used to supply hydrogen to fuel cell stacks.

[0075] Figure 3 A view illustrating the dehydrogenation reaction system connected to a fuel cell is shown. References will then be made. Figure 3 Describe in detail the dehydrogenation reaction system connected to the fuel cell.

[0076] refer to Figure 3 The dehydrogenation reaction system 10 includes a dehydrogenation reactor 110, an acidic aqueous solution tank 120, and a fuel cell stack 500, and may optionally include a gas cooler 300 and a buffer tank 400.

[0077] Since the descriptions of the dehydrogenation reactor 110 and the acidic aqueous solution tank 120 are the same as those described above, the repeated descriptions are omitted.

[0078] The dehydrogenation reactor 110 can increase the hydrogen storage capacity by setting up multiple reactors side by side as needed.

[0079] The hydrogen produced by the dehydrogenation reactor 110 is transferred to the gas cooler 300. The gas cooler 300 cools the supplied hydrogen. In this application, the cooling temperature of the hydrogen is not particularly limited; as an example, it can be room temperature from 10°C to 60°C.

[0080] Figure 3 The gas cooler 300 is shown to consist of a plurality of chambers connected in sequence to each other, but this application is not limited thereto, and the gas cooler 300 may consist of a single chamber.

[0081] Hydrogen gas cooled in gas cooler 300 is transferred to buffer tank 400. Buffer tank 400 receives and stores a certain amount of hydrogen gas.

[0082] If useful, pressure regulators 610 and 620, or combinations thereof, may also be included between the dehydrogenation reactor 110 and the gas cooler 300, between the gas cooler 300 and the buffer tank 400, and between the buffer tank 400 and the fuel cell stack 500. Sensors (temperature or pressure sensors) may also be included inside or outside the dehydrogenation reactor 110. A mass flow meter 630 may also be included between the buffer tank 400 and the fuel cell stack 500. Therefore, hydrogen can be stored at a constant pressure in the buffer tank 400 and can be supplied to the fuel cell stack 500 at the desired pressure and mass.

[0083] Meanwhile, as described above, the acidic aqueous solution tank 120 can be pressurized using hydrogen produced by the dehydrogenation reactor 110, and the acidic aqueous solution tank 120 can receive hydrogen directly from the dehydrogenation reactor 110, or from the gas cooler 300, the buffer tank 400, or a combination thereof. In this case, the amount of hydrogen supplied to the acidic aqueous solution tank 120 can be controlled by the valve 720.

[0084] The fuel cell stack 500 is located downstream of the buffer tank 400 to receive hydrogen from the buffer tank 400. For example, hydrogen can be received from the buffer tank 400 through an inlet (e.g., a valve).

[0085] The fuel cell stack 500 produces water and electricity simultaneously through the reaction of supplied hydrogen and oxygen. The water produced by the fuel cell stack 500 is discharged through a discharge device (e.g., a valve). The water discharged from the fuel cell stack 500 is then recycled to the acidic aqueous solution tank 120, the dehydrogenation reactor 110, a separate water tank, or all of these devices, thereby increasing hydrogen production efficiency. The amount of water supplied to the acidic aqueous solution tank 120 or the dehydrogenation reactor 110 can be controlled via valves 730 and 740.

[0086] The fuel cell stack 500 can be any device capable of converting hydrogen into usable electrical energy, such as a proton exchange membrane fuel cell (PEMFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC), molten carbonate fuel cell (MCFC), or solid oxide fuel cell (SOFC), but this application is not limited thereto.

[0087] For example, the electrical energy generated by the fuel cell stack 500 can be transmitted through a power converter, such as a DC converter, inverter, or charge controller. The power converter can output a portion of the electrical energy to electrical loads via load interconnects, and another portion can be fed back to the energy storage unit via charging interconnects. The remaining electrical energy can be used to power the control unit.

[0088] The dehydrogenation reaction system 10 prevents water evaporation and reduces the amount of water used by operating the dehydrogenation reactor 110 at high temperature and high pressure. Therefore, a separate gas-liquid separator is not required because the hydrogen does not contain excess water after the reaction.

[0089] In the dehydrogenation reaction system 10, pumps can be used as little as possible by supplying the acidic aqueous solution to the bottom of the dehydrogenation reactor 110 by gravity from the acidic aqueous solution tank 120; however, pumps, filters, or both may be included if necessary.

[0090] For example, a pump can be used to supply the acidic aqueous solution from the acidic aqueous solution tank 120 to the dehydrogenation reactor 110, supply the hydrogen produced by the dehydrogenation reactor 110 to the gas cooler 300, cool the hydrogen supply buffer tank 400 in the gas cooler 300, supply the hydrogen stored in the buffer tank 400 to the fuel cell stack 500, supply hydrogen to the acidic aqueous solution tank 120, or supply the water produced by the fuel cell stack 500 to the dehydrogenation reactor 110 or the acidic aqueous solution tank 120.

[0091] The filter can substantially remove unwanted particles contained in the hydrogen by filtering the produced hydrogen. The filter can be located between the dehydrogenation reactor 110, the gas cooler 300, the buffer tank 400, and the fuel cell stack 500, particularly between the buffer tank 400 and the fuel cell stack 500.

[0092] In addition, optionally, the dehydrogenation reaction system 10 may include an outlet for discharging a mixture of chemical hydrides, acids and water after the reaction is complete, and may include means for removing reaction byproducts other than hydrogen and water or converting them into other materials.

[0093] The following illustrates specific embodiments of this application. However, the embodiments described below are intended only to illustrate or describe this application and should not limit the scope of this application.

[0094] (Evaluation methods for dehydrogenation reactions)

[0095] Chemical hydride 111 is loaded into high-temperature, high-pressure dehydrogenation reactor 110. An acidic aqueous solution mixed in a specific molar ratio is injected using a syringe or high-pressure pump. The injection rate can be adjusted from 0.01 mL / min to 20 mL / min, and can vary depending on the size of the dehydrogenation reactor 110 and the amount of chemical hydride 111.

[0096] Pressure and temperature are measured and maintained at the predetermined pressure and temperature through valve control and cooling. In some cases, H2O can be injected first, followed by acid.

[0097] The hydrogen conversion rate can be calculated using Equation 1 below, and the flow rate and purity can be measured using a mass flow meter and gas chromatography (GC).

[0098] [Equation 1]

[0099] Hydrogen conversion rate = (Amount of hydrogen discharged from the reactor via mass flow meter + (Pressure at room temperature after reaction) × (Reactor volume)) / (Theoretical hydrogen production)

[0100] (Implementation Plan 1)

[0101] Using a dehydrogenation reaction system 10, under room temperature and indoor pressure conditions, a dehydrogenation reaction was carried out using NaBH4 as the chemical hydride 111 and HCOOH as the acid. Simultaneously, the molar ratio of NaBH4:αHCOOH:βH2O was changed to 0≤α≤1, 3≤β≤4, and α+β=4 to measure the hydrogen storage capacity (H2 storage capacity, wt%). The results are shown in... Figure 4 middle.

[0102] refer to Figure 4 In embodiment 1, the reaction is carried out under room temperature / indoor pressure conditions according to the following reaction formula 2, the total molar sum of HCOOH and H2O is kept at 4 (e.g., to minimize the amount of water used), and as a result of the reaction, it is determined that hydrogen is produced under conditions of 0.25 moles to 1 mole of HCOOH, and in particular, hydrogen close to the theoretical storage amount is produced at 0.5 moles.

[0103] [Reaction 2]

[0104] NaBH4+αHCOOH+βH2O->αHCOONa+ Na x B y O z γH₂O + 4H₂↑

[0105] (Implementation Plan 2)

[0106] The reaction molar ratio of NaBH4:αHCOOH:βH2O was fixed at α=0.5 and β=3.5. Simultaneously, the temperature was varied from 25℃ to 300℃, and the pressure from 1 bar to 50 bar. The hydrogen storage capacity was measured, and the results showed... Figure 5 middle.

[0107] refer to Figure 5 In order to obtain the same amount of hydrogen production as the theoretical value by preventing water evaporation, the reaction temperature and pressure were increased. As a result, the optimal reaction conditions were determined, and the hydrogen storage capacity was determined to be 6% by weight or higher (theoretical value: 6.5% by weight) at a temperature of 100°C to 250°C and a pressure of 5 bar to 50 bar. In particular, 100% conversion was achieved in the range of 100°C to 250°C and 30 bar to 50 bar.

[0108] (Implementation Plan 3)

[0109] Under conditions of 180℃ and 30 bar, the molar ratio of NaBH4:αHCOOH:βH2O was changed to α=0.5 and 2≤β≤4, and the hydrogen storage capacity was measured. The results show... Figure 6 middle.

[0110] refer to Figure 6 As a result of the examination of the conditions for minimizing water usage under high temperature / high pressure conditions, with 0.5 moles of HCOOH, H2O can be reduced to 2 moles, and the hydrogen storage capacity can theoretically reach 8.3% by weight, and experimentally reach 7.0% by weight (room temperature / indoor pressure conditions: 5.5% by weight).

[0111] (Implementation Plan 4)

[0112] Under conditions of 180℃ and 30 bar, the molar ratio of NaBH4:αHCOOH:βH2O was changed to 0≤α≤0.7, 1.8≤β≤2.5, and α+β=2.5. The hydrogen storage capacity was measured, and the results showed... Figure 7 middle.

[0113] refer to Figure 7 In order to minimize water usage, after fixing the total molar ratio of HCOOH and H2O at 2.5, the hydrogen storage capacity was determined to be 6% by weight or higher in the range of 0.3 to 0.5 mol of HCOOH, based on the results of measuring the amount of hydrogen produced according to the molar ratio of HCOOH.

[0114] (Implementation Plan 5)

[0115] The molar ratio of NaBH4:HCOOH:H2O was changed to 1:0.5:3.5, 1:0.75:3.25, and 1:1:3 under room temperature and atmospheric pressure conditions, and the conversion rate was measured. The results show... Figure 8 The results are summarized in Table 1.

[0116] exist Figure 8 In the figure, SBH represents NaBH4 and FA represents HCOOH. Among the two results with a molar ratio of 1:0.5:3.5, the first result is the result of mixing FA and H2O, and the second result is the result of injecting FA after injecting H2O.

[0117] (Table 1)

[0118]

[0119] refer to Figure 8 According to Table 1, when the total molar ratio of HCOOH to H2O is fixed at 4 and the molar ratio is changed, the optimal hydrogen conversion rate (hydrogen storage capacity of 5.5% by weight) is determined when the molar ratio of HCOOH is 0.5.

[0120] (Implementation Plan 6)

[0121] For the molar ratios of NaBH4:HCOOH:H2O of 1:0.5:3.5 and 1:0.3:2.2, the conversion rate was measured by changing the reaction temperature from 25℃ to 180℃ at 30 bar. The results show... Figure 9 The results are summarized in Table 2.

[0122] exist Figure 9 In the above, ⓐ represents the case with a molar ratio of 1:0.5:3.5 (theoretical H2 storage capacity: 6.5 wt%), and ⓑ represents the case with a molar ratio of 1:0.3:2.2 (theoretical H2 storage capacity: 8.8 wt%).

[0123] (Table 2)

[0124]

[0125] refer to Figure 9 As shown in Table 2, when evaluated as a high-temperature / high-pressure reactor, it can be determined that the hydrogen conversion rate increases by 22% to 43%, depending on the reaction molar ratio.

[0126] (Implementation Plan 7)

[0127] To determine the change in hydrogen conversion rate when using a catalyst, the conversion rate (theoretical H2 stock: 4.32 wt%) was measured by injecting a catalyst containing 2.6 mg of Ru(acac)3 and 1 mL of THF (where the molar ratio of NaBH4:Ru(acac)3 = 800:1), where the molar ratio of NaBH4:HCOOH:H2O was 1:0.5:3.5.

[0128] exist Figure 10 In the diagram, SBH represents NaBH4, FA represents HCOOH, ① represents the FA+H2O injection time, ② represents the FA+H2O injection stop time, and ③ represents the catalyst injection time.

[0129] (Table 3)

[0130]

[0131] refer to Figure 10 According to Table 3, the conversion rate increased from 87% (before catalyst injection) to 95% (after catalyst injection).

[0132] (Implementation Plan 8)

[0133] The reaction conditions were changed as shown in Table 4 below, and the dehydrogenation reaction was carried out. The results are also summarized in Table 4.

[0134] (Table 4)

[0135]

[0136] Referring to Table 4, it can be determined that by preventing water evaporation and improving reactivity under high temperature / high pressure conditions, the hydrogen production increases to 6.9% by weight, and it can be determined that by using Ru(acac)3 catalyst, the hydrogen production increases to 7.0% by weight.

[0137] (Implementation Plan 9)

[0138] As shown in reactions 3 and 4 below, the activities of weak acids (HCOOH) and strong acids (H2SO4, HCl) in solutions with the same pH were compared, and the results are shown in Table 5.

[0139] [Reaction 3]

[0140] NaBH4+0.5HCOOH+3.5H2O->0.5HCOONa+0.5H3BO3+4H2+0.5NaB(OH)4 (pH=2)

[0141] [Reaction 4]

[0142] NaBH4+0.00381HCl+3.99619H2O->0.00381NaCl+0.99619NaB(OH)4+0.00381B(OH)3+4H2

[0143] (Table 5)

[0144]

[0145] Referring to Table 5, it can be determined that using HCOOH at the same pH is advantageous in terms of hydrogen storage capacity compared to strong acids. Furthermore, in the case of strong acids, it can be determined that using excess water when increasing the pH of the solution leads to a decrease in hydrogen storage capacity. Therefore, it can be determined that activating the weak acid HCOOH can achieve safety and reduce system corrosion problems.

[0146] Although this application has been described in conjunction with embodiments now considered practical, it should be understood that this application is not limited to the disclosed embodiments. Rather, this application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0147] Figure label description

[0148] 10: Dehydrogenation reaction system

[0149] 100: Dehydrogenation reaction unit

[0150] 110: Dehydrogenation reactor

[0151] 111: Chemical hydrides

[0152] 112: Porous foam metal

[0153] 120: Acidic aqueous solution tank

[0154] 230: Cooling equipment

[0155] 300: Gas Cooler

[0156] 400: Buffer tank

[0157] 500: Fuel Cell Stack

[0158] 610, 620: Pressure regulator

[0159] 630: Mass Flow Meter

[0160] 710, 720, 730, 740: Valves

Claims

1. A method for generating hydrogen, the method comprising: Hydrogen gas is produced through the dehydrogenation reaction of solid chemical hydrides with acidic aqueous solutions. The dehydrogenation reaction is carried out by reacting the hydrogen atoms of a chemical hydride with acid and water, wherein the molar ratio of chemical hydride:acid:water is 1:0.5 to 0.3:3.5 to 2.

2. The dehydrogenation reaction occurs at temperatures ranging from 100°C to 400°C and pressures ranging from 1 bar to 100 bar. The chemical hydride includes NaBH4, and The acid includes formic acid.

2. The hydrogen generation method according to claim 1, wherein, The dehydrogenation reaction is carried out in the presence of a homogeneous catalyst, which includes ruthenium acetylacetonate (III), carbonyl chloride hydrogen {bis[2-(diphenylphosphinomethyl)ethyl]amino}ruthenium (II), ruthenium triphenylphosphine monosulfonate (II), ruthenium benzene (II), or combinations thereof.

3. The hydrogen generation method according to claim 1, wherein, The gaseous products produced in the dehydrogenation reaction contain 99% or more hydrogen and 1% or less water.

4. The hydrogen generation method according to claim 1, wherein, The dehydrogenation reaction is carried out in a dehydrogenation reactor comprising a dehydrogenation reactor and an acidic aqueous solution tank. The dehydrogenation reactor contains a solid chemical hydride, and the acidic aqueous solution tank supplies acidic aqueous solution to the dehydrogenation reactor. The dehydrogenation reactor includes a heating device, a cooling device, porous foam metal, or a combination thereof.

5. The hydrogen generation method according to claim 4, wherein, The porous foam metal is porous foam nickel or porous foam cobalt-nickel.

6. The hydrogen generation method according to claim 4, wherein, An acidic aqueous solution is supplied to the dehydrogenation reactor by gravity or a pump.

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