Process, plant, aqueous solution, and electrode for the production of hydrogen and method for coating electrode

Abstract

A process for producing hydrogen from an aqueous solution containing hydrochloric acid in its dissociated form, wherein the aqueous solution contains at least one electrode composed of a metal alloy comprising a plurality of metals having different standard reduction potentials, the process comprising the steps of: reducing hydrated hydrogen ions present in the solution to hydrogen, thereby generating an electron flow from the lower potential metal to the higher potential metal in the electrode between the metal pairs, and extracting the hydrogen thus obtained from the aqueous solution.

Description

[Technical Field]

[0001] This invention relates to a process for producing hydrogen. [Previous Technology]

[0002] Hydrogen is currently an important raw material used in the chemical and oil refining industries. Due to its low environmental impact and high energy content, there is also increasing interest in using hydrogen as a fuel.

[0003] The most common method for large-scale hydrogen production currently involves using hydrocarbons and fossil fuels as starting materials.

[0004] The main hydrocarbon conversion process is vapor reforming, which involves the endothermic catalytic conversion of light hydrocarbons (e.g., methane) in the presence of water vapor.

[0005] Other processes involve partial oxidation, in which heavy hydrocarbons (e.g., heavy oil residues from the petrochemical industry) are subjected to heat treatment in the presence of oxygen.

[0006] However, the mining of hydrocarbons has a very negative impact on the environment because it releases large amounts of carbon dioxide into the atmosphere, leading to an increase in the Earth's thermal balance and the greenhouse effect.

[0007] Several technologies for producing hydrogen are currently being researched, taking into account the availability of carbon dioxide at different times.

[0008] One such technology is water electrolysis. However, this technology has many drawbacks due to the limited amount of hydrogen produced and the high cost of electricity. For these reasons, the amount of hydrogen produced by the water electrolysis process is currently negligible.

[0009] Hydrogen can also be obtained from water through biological production or by thermal decomposition using heat. However, these technologies are even inefficient for large-scale hydrogen production.

[0010] Therefore, there is an urgent need to develop more energy-efficient processes for producing large quantities of hydrogen that can reduce carbon dioxide emissions into the atmosphere and reduce costs. [Summary of the Invention]

[0011] The present invention aims to provide a process for producing large quantities of hydrogen in a manner with low energy consumption and low environmental impact.

[0012] This can be accomplished according to the process method of request item 1.

[0013] According to the process of the present invention, hydrogen is produced from an aqueous solution containing hydrochloric acid in a dissociated form, the aqueous solution containing hydrated hydrogen ions (H3O+), the aqueous solution containing at least one electrode composed of a metal alloy comprising a plurality of metals having different standard reduction potentials, the process comprising the following steps: reducing hydrated hydrogen ions (H3O+) present in the solution to hydrogen gas (H2), thereby generating an electron flow from the lower potential metal to the higher potential metal in the at least one electrode between the metal pairs, and extracting the hydrogen gas thus obtained from the aqueous solution.

[0014] The aqueous solution is prepared by introducing hydrochloric acid into water, which dissociates and releases hydrated hydrogen ions (H3O+) and forms chloride ions (Cl-) according to the following equation: HCl + H2O → H3O++ Cl- (1) The standard reduction potential (E0) is a measure of the tendency of a chemical species to gain electrons (i.e., to be reduced). The higher the E0 value, the higher the electron affinity of the species and the more likely the species is to be reduced. The standard reduction potential (E0) is defined relative to the standard hydrogen electrode with a potential of E0 = 0.00 V and is measured under standard conditions, i.e., at a temperature of 298 K (25 °C) and a pressure of 100 kPa (1 bar).

[0015] The potential difference between each metal pair must be large enough to ensure that this electron flow migrates from the lower potential metal to the higher potential metal. Preferably, the potential difference is equal to at least 0.20 Volt, more preferably, at least 0.50 Volt.

[0016] In each metal pair in which the electron flow is generated, the metal that releases electrons acts as the anode and is oxidized according to the following half-reaction as a reducing agent: M → Mn++ ne- (2) "n" is an integer, preferably 2 or 3.

[0017] The metal that receives electrons is instead an inert cathode, at which H3O+ ions present in the solution act as oxidants and gain electrons according to the following half-reaction: 2H++ 2e-→ H2 (3) In particular, the following redox reaction occurs on the at least one electrode: H2O (l) → O2(g) + 2H2(g) (4) This results in the formation of hydrogen gas together with oxygen.

[0018] The metal alloy forming the at least one electrode preferably comprises magnesium and at least one of the following metals: beryllium (Be), aluminum (Al), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), silicon (Si), and nickel (Ni).

[0019] In a preferred embodiment, the metal alloy primarily comprises magnesium. In a particular preferred embodiment, the metal alloy comprises a magnesium content ranging from 85% to 95% by weight, preferably from 90% to 91% by weight.

[0020] Magnesium is the metal with the lowest standard reduction potential among the plurality of metals, and therefore has the greatest tendency to transfer electrons. Thus, when the metal alloy comes into contact with an aqueous solution, electron migration occurs from magnesium to each of the plurality of metals. Thus, magnesium always acts as the anode, oxidized according to the half-reaction (1), where the value of n is 2.

[0021] Silicon is the metal with the highest standard reduction potential in the group of metals, so silicon always acts as an inert cathode, in which, according to half reaction (2), hydrated hydrogen ions present in the solution gain electrons and form hydrogen gas.

[0022] Depending on the metal in which electron exchange occurs, each metal having a moderate standard reduction potential between Mg and Si serves as either an inert cathode or an anode for oxidation according to half-reaction (1). When half-reaction (1) involves metals such as Be, Mn, Zn, Fe, Cu and Ni, the value of n is assumed to be 2; conversely, when half-reaction (1) involves metals such as Al, the value of n is assumed to be 3.

[0023] In a preferred embodiment of the present invention, the metal alloy has the following composition in weight percentage (%): 90.81% Mg, 5.83% Al, 2.85% Zn, 0.45% Mn, 0.046% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, and 0.00050% Ni.

[0024] According to other embodiments of the present invention, the metal alloy has the following composition in weight percentages (%): 90.65% Mg, 5.92% Al, 2.92% Zn, 0.46% Mn, 0.043% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, and 0.00050% Ni.

[0025] According to a particularly advantageous embodiment of the invention, the outer surface of the at least one electrode is coated with a coating containing at least one metal fluoride, specifically magnesium fluoride, aluminum fluoride and / or zinc fluoride.

[0026] Preferably, the at least one electrode system is externally coated with a coating comprising one or more of the aforementioned metal fluorides mixed with methacrylic resin. Even more preferably, the methacrylic resin comprises 50% to 70% (by weight) PFTE, 15% to 25% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1), and 15% to 25% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

[0027] According to a preferred embodiment of the present invention, the methacrylate resin comprises 60% (by weight) PFTE, 20% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 20% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

[0028] Preferably, the coating of the at least one electrode has a thickness of 0.5 mm to 3.0 mm, more preferably 1.0 mm to 2.0 mm.

[0029] According to a more preferred embodiment of the invention, a graphite member is provided at one end of the at least one electrode, the graphite member not being covered by the aforementioned coating on the outer surface of the electrode.

[0030] Advantageously, a metal component, such as an iron or carbon steel rod, is also provided inside at least one electrode, which contacts the graphite component of the electrode.

[0031] According to yet another embodiment of the invention, the outer coating of the at least one electrode is covered with a perforated tape or PTFE mesh. Preferably, the tape or PTFE mesh applied to the coating has a thickness of several micrometers, for example, 1 to 3 µm.

[0032] According to another embodiment of the invention, the outer coating of the at least one electrode is covered with a semi-permeable tape, which is permeable to an aqueous solution flowing toward the electrode but impermeable to an aqueous solution flowing in the opposite direction. The tape is also permeable to hydrogen.

[0033] The aforementioned aqueous solution is prepared by introducing hydrochloric acid into water to form a mixture. Preferably, the mixture contains hydrochloric acid in an amount between 5% and 10%, more preferably between 6% and 7%. The percentage values ​​are by volume.

[0034] The percentage of hydrochloric acid in the aqueous solution causes the process of the present invention to be carried out in an acidic environment. The pH at which the process occurs is preferably in the range of 2 to 4, and more preferably in the range of 2 to 3.4.

[0035] The process is preferably carried out at a temperature in the range of 20 to 70°C, and more preferably in the range of 55 to 60°C.

[0036] Preferably, the process is carried out at a pressure below atmospheric pressure, for example, between 0.3 and 0.5 bar absolute.

[0037] Due to the low molecular weight of hydrogen, the hydrogen thus obtained is spontaneously released from the solution.

[0038] Given the high molecular weight of oxygen, the oxygen generated during the process will instead remain in the aqueous solution and will tend to bond with chlorine, which is also present in the aqueous solution, to form hypochlorous acid (HClO).

[0039] According to a preferred embodiment of the invention, in order to avoid the accumulation of hypochlorous acid in the aqueous solution, the latter is advantageously regenerated by means of a recycling step and a degassing step of the aqueous solution, which are adapted to extract oxygen generated together with hydrogen during the reduction step of the aforementioned reference half-reaction (3). The degassing step includes a filtration step, during which oxygen is removed.

[0040] Specifically, a porous baffle membrane filter filled with MnO2 is preferably used to perform the filtration step, during which oxygen (O2) and chlorine (Cl2) are released separately. Preferably, the chlorine is then introduced into an aqueous solution in a foaming manner to recover the chlorine.

[0041] Preferably, the degassing step is performed under vacuum.

[0042] Since the reaction that forms the basis of the process according to the present invention is exothermic, the recycling step preferably also includes a step of cooling the aqueous solution, which is suitable for maintaining the reaction temperature within the aforementioned range.

[0043] Other aspects of the invention relate to apparatus for producing hydrogen according to the aforementioned process. This apparatus comprises: at least one buffer tank for storing an aqueous solution containing hydrochloric acid in its dissociated form; at least one reactor for producing hydrogen, wherein at least one electrode is placed in the at least one reactor, the at least one electrode being composed of a metal alloy comprising a plurality of metals having different standard reduction potentials; at least one feed line for supplying the aqueous solution from the at least one buffer tank to the at least one reactor; at least one recirculation line for recirculating the aqueous solution from the at least one reactor to the at least one buffer tank; at least one device for regenerating the aqueous solution, the device being arranged along the at least one recirculation line; and components for extracting hydrogen from the at least one reactor.

[0044] Preferably, the regeneration device includes a filtration device, such as at least one porous baffle membrane filter preferably filled with MnO2, suitable for separating oxygen (O2) formed during hydrogen production in the at least one reactor (degassing). Preferably, the filtration device operates under vacuum.

[0045] Preferably, the apparatus according to the invention also includes at least one cooling device along the recirculation line, including at least one heat exchanger adapted to cool the aqueous solution effluent from the at least one reactor and maintain the reaction temperature in the range of 20 to 70°C.

[0046] According to a particular advantageous embodiment, the cooling device is disposed upstream of the regeneration device.

[0047] In some embodiments, the apparatus includes two parallel reactors, each reactor having a separate feed and recirculation line for the aqueous solution, a separate device for regenerating the aqueous solution in the recirculation line, and a separate hydrogen extraction component.

[0048] Other aspects of the present invention relate to electrodes made of metal alloys used in the aforementioned hydrogen production process. For details regarding the composition of the metal alloy used to manufacture the electrode, the actual structure of the electrode, and the electrode coating, please refer to the description related to the process.

[0049] The subject of this invention is also an aqueous solution used in the aforementioned hydrogen production process, comprising hydrated hydrogen ions (H3O+) and chloride ions (Cl-).

[0050] Another aspect of the present invention is a method for coating the outer surface of the at least one electrode.

[0051] The method comprises: - a step involving immersing the at least one electrode in a hydrofluoric acid and water bath, wherein a metal constituting the outer surface of the electrode reacts with the hydrofluoric acid to form a metal fluoride salt of fluorinated patina; - a first step of drying the metal fluoride salt of the fluorinated patina; - a step of applying a methacrylic resin gel onto the fluorinated patina, the methacrylic resin belonging to the type described in relation to the process; - a second step of drying the mixture thus obtained comprising the metal fluoride and the methacrylic resin to obtain an outer coating of the electrode.

[0052] Preferably, the second drying step has a time range of 10 to 16 hours, more preferably 12 hours.

[0053] According to a preferred embodiment of the invention, the method of coating the electrode further relates to covering the electrode with a perforated tape or PTFE mesh at the end of the second drying step. Preferably, the tape or PTFE mesh has a thickness of several micrometers, for example, 1 to 3 µm.

[0054] According to another embodiment of the invention, the step of coating the electrode is performed using a semi-permeable webbing that is permeable to an aqueous solution flowing toward the electrode but impermeable to an aqueous solution flowing in the opposite direction. The webbing is also permeable to hydrogen.

[0055] The advantages of the present invention are that it provides a process for producing large quantities of hydrogen, since hydrogen can be obtained substantially without external input of heat and electricity, thus the present invention has low energy consumption; since this process does not release CO2 into the atmosphere, the present invention has low environmental impact; and since hydrochloric acid is a commercially available substance, the present invention is low cost.

[0056] The advantages of the present invention will be more clearly demonstrated by the following embodiments, which are preferred embodiments provided in a non-limiting manner.

Implementation Method

[0059] Figure 1 shows equipment 100 for continuous hydrogen production. Equipment 100 substantially includes a buffer tank 1 for storing an aqueous solution 20; two reactors 2 and 3 for producing hydrogen, the two reactors 2 and 3 being identical and arranged in parallel; individual pipelines 21, 22 and 21, 23 for supplying the aqueous solution from the buffer tank 1 to the reactors 2 and 3; and components 4 and 5, for example, conventional effluent conduits, for extracting the hydrogen produced in the aforementioned reactors 2 and 3.

[0060] Each reactor 2 and 3 contains a cartridge, denoted by element symbols 6 and 7 respectively, containing a plurality of electrodes made of a metal alloy composed of metals having different standard reduction potentials.

[0061] The metal alloy comprises magnesium and at least one of the following metals: beryllium (Be), aluminum (Al), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), silicon (Si), and nickel (Ni). Preferably, the magnesium content is in the range of 85% to 95% by weight, more preferably 90% to 91% by weight.

[0062] The electrode is obtained from the aforementioned metal in particulate form according to the following process, wherein the metal is mixed and heated until it is completely melted, and wherein the resulting melt is cast into a specific mold, the melt being cooled and solidified inside the specific mold. Finally, the electrode according to the invention is removed from the mold.

[0063] According to a preferred embodiment of the invention, a metal component, such as an iron or carbon steel rod, is placed inside the mold before casting the molten metal. Preferably, the metal component is placed inside the mold such that the end portion of the metal component does not contact the molten metal. Once the molten metal has cooled and the electrode has been removed from the mold, the end portion of the aforementioned metal component will be located outside the electrode and protrude from the electrode.

[0064] A preferred embodiment of the electrode according to the present invention is shown in Figure 2.

[0065] Figure 2 schematically shows an electrode 200 comprising a substantial cylinder 201 made of the metal alloy and having a metal rod 202 housed therein. At a terminal portion 203, the rod 202 protrudes from the cylinder 201. The terminal portion 203 has a graphite member 204 fixed to it. Preferably, the graphite member is screwed onto the terminal portion of the rod 202, and a plastic washer 205 is placed between the graphite member 204 and the cylinder 201. This creates contact between the graphite member 203 and the rod 202.

[0066] The cylinder 201 also has an outer coating, usually indicated by component symbol 206, and includes a layer 207 of at least one metal fluoride mixed with methacrylate resin 208, the metal fluoride being in particular magnesium fluoride, aluminum fluoride and / or zinc fluoride, and the methacrylate resin 208 is preferably 60% (by weight) PFTE, 20% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 20% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

[0067] It is also advantageous to cover the outer coating 206, which is composed of at least one metal fluoride and methacrylic resin, with a perforated tape or PTFE mesh 209 having a thickness of several micrometers, for example 1 to 3 µm.

[0068] In the example of Figure 1, the electrodes and cartridges 6 and 7 are respectively placed inside reactors 2 and 3, in the protruding positions relative to the bottom.

[0069] Each reactor 2 and 3 is in fluid communication with buffer tank 1 via individual lines 26, 28 and 27, 28 for recirculating an aqueous solution, which is then processed by a series of devices. Specifically, each reactor 2 and 3 is in fluid communication with cooling devices 8 and 9 via the aforementioned recirculation lines, which consist of at least one heat exchanger (not shown). The aqueous solution from cooling devices 8 and 9 flows to a filtration device 10, which includes a porous baffle membrane filter preferably filled with MnO2 (not shown) capable of separating oxygen (O2) formed during hydrogen production in reactors 2 and 3 (degassing).

[0070] Each recirculation line 26, 28, 27, 28 is internally connected to reactors 2 and 3 via discharge conduits 12 and 13, which extend substantially to the bottom of the reactors. Specifically, the openings of the discharge conduits 12 and 13 are located below cartridges 6 and 7, between the bottom of reactors 2 and 3 and the base of the cartridge itself.

[0071] The equipment also has one or more pipelines for internal circulation of the aqueous solution present in the buffer tank 1. Depending on the requirements, these pipelines can be connected via individual connecting pipes to pipelines for supplying the aqueous solution to the reactor. In the example shown in Figure 1, the two internal circulation pipelines 24 and 25 are connected to supply pipelines 22 and 23 via individual connecting pipes 24b and 25b.

[0072] The equipment also includes section 14, located upstream of buffer tank 1, in which hydrochloric acid solution 40 and tap water 41 are mixed to prepare aqueous solution 20. Section 14 substantially includes tank 15 for storing acid solution 40, device 16 for filtering tap water, and pipeline 42 for supplying filtered water.

[0073] The flow of tap water 41 is controlled by valve V1 located upstream of filter device 16 and check valve V2 located downstream of filter device 16. Instead, solution 40 is pumped by pneumatic pump P1 connected to tank 15. When buffer tank 1 is filled, pneumatic pump P1 is started and pneumatic valve V3 is opened. Then, solution 40 passes through check valve V4 and mixes with filtered tap water 42 to form the aforementioned aqueous solution 20.

[0074] The aqueous solution 20 preferably contains hydrochloric acid in an amount between 3 and 20% by volume, and hydrochloric acid in an amount between 5 and 10% by volume, preferably between 6 and 7% by volume.

[0075] During use, the equipment 100 is operated as follows: The buffer tank 1 is filled with an aqueous solution 20. The aqueous solution is then supplied to reactors 2 and 3 until individual liquid levels L1 and L2 are reached.

[0076] Referring more specifically to the example shown in Figure 1, the aqueous solution leaving the buffer tank 1 via pipeline 21 is pumped by pump P2, and conveyed through flow meter 17 which controls the filling of reactors 2 and 3. The aqueous solution is then divided into two parts, which are supplied to reactors 2 and 3 via pipelines 22 and 23 through individual pneumatic valves V6 and V7.

[0077] Once the reactor is filled, the aqueous solution remains inside the reactor for a predetermined time, preferably within a few minutes, and the reaction proceeds in the presence of electrodes to supply hydrogen and oxygen together according to reaction (4): H2O(l) → O2(g) + 2H2(g). The reaction temperature is preferably between 55 and 60 °C and the pressure is between 2.5 and 3 bar.

[0078] Due to the low molecular weight of hydrogen, the hydrogen thus obtained is released from the solution and accumulates in the collection chambers inside reactors 2 and 3, which are located between the liquid levels L1 and L2 and the lids of the individual reactors. The hydrogen accumulated in the chambers is extracted from reactors 2 and 3 via individual discharge conduits 4 and 5 and stored in appropriate tanks (not shown).

[0079] Instead, the aqueous solution is extracted via individual discharge conduits 12 and 13 and recirculated in recirculation lines 26 and 27. The extraction of the aqueous solution is controlled by pneumatic valves V5 and V6, and the opening of pneumatic valves V5 and V6 is controlled by the liquid levels L1 and L2 in reactors 2 and 3.

[0080] The openings of the discharge conduits 12 and 13 are lower than those of the cartridges 6 and 7, so that the hydrogen gas formed at the electrodes will not be drawn into the recirculation lines 26 and 27 along with the aqueous solution.

[0081] The aqueous solution extracted from the reactor via recirculation lines 26 and 27 is first cooled in the heat exchangers of cooling devices 8 and 9 by means of indirect heat exchange with cooling water flow (not shown). The aqueous solution circulating in recirculation lines 26 and 27 is cooled so that a constant temperature between 55 and 60°C is maintained inside reactors 2 and 3.

[0082] The cooled aqueous solution then undergoes a degassing step to extract oxygen from the aqueous solution. This degassing step includes a filtration step, preferably performed under vacuum inside the filtration device 10. Oxygen is thus separated from the aqueous solution and extracted via a specific discharge conduit 32. The term "under vacuum" refers to a pressure slightly less than 1 bar, for example, between 0.5 and 0.8 bar.

[0083] During the filtration process performed inside device 10 using a porous baffle membrane filter preferably filled with MnO2 (not shown), chlorine (Cl2) is released in addition to oxygen. The chlorine is then preferably introduced into an aqueous solution in a foaming manner to recover it.

[0084] The aqueous solution, which does not contain oxygen, is then recirculated to the buffer tank 1 via the recirculation line 28.

[0085] The aqueous solution 20 is continuously introduced from the buffer tank 1 into reactors 2 and 3 via supply lines 21, 22 and 21, 23 to maintain constant liquid levels L1 and L2. The aqueous solution 20 is kept in a constant flow by recirculating it through internal circulation lines 24 and 25. To allow recirculation, the aqueous solution is pumped via individual pumps P3 and P4.

[0086] During operations involving inspection or maintenance of reactors 2 and 3, the latter are emptied via individual channels 29 and 30, and the aqueous solution is fed in a stream 31 to a waste collection tank (not shown). During these operations, electrode regeneration may be performed if necessary. Specifically, the outer coating 206 of the electrodes may be restored by immersing them in an aqueous solution containing hydrofluoric acid for an appropriate period of time (e.g., 10 to 20 minutes, preferably 15 minutes).

[0087] If necessary, during the operation of the equipment, a portion of the aqueous solution circulating in the internal circulation lines 24 and 25 will be supplied to reactors 2 and 3 via individual pipes 24b and 25b, which are connected to the internal circulation lines 24 and 25 and the individual supply lines 22 and 23.

[0088] The equipment used in the machine is advantageously sealed, preferably made of steel, and the buffer tank 1, in addition to the filter device 10, also operates under vacuum. In this case, the pressure inside the buffer tank 1 is between 0.03 and 0.08 bar. This prevents oxygen present in the aqueous solution from coming into contact with the outside air.

[0089] The following describes an example of the execution of the process according to the present invention.

[0090] Example

[0091] Two identical cylindrical reactors with a height of 120 cm and a diameter of 30 cm are used.

[0092] In each reactor, a cartridge containing 32 electrodes is introduced. These electrodes are also cylindrical, with a height of 40 cm and a diameter of 4 cm, and are made of a metal alloy composed of the following: 90.81% Mg, 5.83% Al, 2.85% Zn, 0.45% Mn, 0.046% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, and 0.00050% Ni.

[0093] Set the cartridge at a height of about 20 cm from the bottom of the reactor.

[0094] Next, each reactor is filled with a solution of a total volume of 25 liters, which contains water and hydrochloric acid.

[0095] The aforementioned solution is prepared by introducing 2.36 liters of 38% hydrochloric acid solution into tap water, such as the amount needed to make up the aforementioned 25 liters.

[0096] Therefore, the solution composition in the reactor is as follows: 26.464 liters of water and 0.896 liters of hydrochloric acid.

[0097] In other words, the mixture contains 96.72% by volume of tap water and 3.28% by volume of hydrochloric acid.

[0098] The residence time of the solution is approximately 15 minutes and it can produce hydrogen gas at a rate of 22 Nm³ / h. This hydrogen production process advantageously achieves an energy consumption of less than 1.5 kWh.

[0099] According to a further embodiment, the process of the present invention also includes providing hydrofluoric acid (HF) to an aqueous solution (20) containing hydrochloric acid in its dissociated form. Preferably, 50 to 70 ml of this hydrofluoric acid (HF) is added to every 10,000 ml of the aqueous solution, more preferably 60 ml.

[0100] In this respect, in addition to hydrated hydrogen ions (H3O+) and chloride ions (Cl-), the aqueous solution used in the process of this invention also contains hydrofluoric acid (HF) in the amount described above. In this aqueous solution, the hydrofluoric acid undergoes ion dissociation.

[0101] By irradiating the electrodes with visible coherent light (especially LED light), particularly satisfactory hydrogen (H2) production results can be obtained, with an increase in yield of up to 20%. [Simplified Explanation of the Diagram]

[0057] Figure 1 shows a diagram of the equipment for producing hydrogen according to a preferred embodiment of the process according to the present invention.

[0058] Figure 2 shows in detail the electrodes according to the machine and equipment diagram in Figure 1. [Biomaterial Storage]

[0103] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A process for producing hydrogen from an aqueous solution (20) containing hydrochloric acid in a dissociated form, the aqueous solution (20) containing hydrated hydrogen ions (H3O+), at least one electrode present in the aqueous solution (20), the at least one electrode being composed of a metal alloy comprising a plurality of metals having different standard reduction potentials, the process comprising the steps of: reducing the hydrated hydrogen ions (H3O+) present in the aqueous solution (20) to hydrogen gas (H2), thereby generating an electron flow in the at least one electrode between metal pairs from the metal having a lower potential to the metal having a higher potential, and extracting the hydrogen gas thus obtained from the aqueous solution (20), wherein the outer surface of the at least one electrode is coated with a coating comprising at least one metal fluoride.

2. The process according to claim 1, wherein the metal alloy comprises magnesium and at least one of the following metals: beryllium (Be), aluminum (Al), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), silicon (Si), and nickel (Ni).

3. The process according to claim 2, wherein the metal alloy primarily comprises magnesium.

4. The process according to claim 3, wherein the metal alloy contains a magnesium content in the range of 85% to 95% by weight.

5. The process according to claim 4, wherein the metal alloy contains a magnesium content in the range of 90% to 91% by weight.

6. According to the process described in claim 2, 3 or 4, the metal alloy of said at least one electrode is composed of the following (by weight): A) 90.81% Mg, 5.83% Al, 2.85% Zn, 0.45% Mn, 0.046% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, 0.00050% Ni; or B) 90.65% Mg, 5.92% Al, 2.92% Zn, 0.46% Mn, 0.043% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, 0.00050% Ni.

7. The process according to claim 1, wherein the at least one metal fluoride comprises magnesium fluoride, aluminum fluoride and / or zinc fluoride.

8. The process according to claim 7, wherein the coating comprises the at least one metal fluoride mixed with a methacrylic resin.

9. The process according to claim 8, wherein the methacrylate resin comprises 50% to 70% (by weight) PFTE, 15% to 25% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 15% to 25% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

10. The process according to claim 9, wherein the methacrylate resin comprises 60% (by weight) PFTE, 20% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 20% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

11. The process according to claim 7, wherein the coating of the at least one electrode has a thickness of 0.5 mm to 3.0 mm.

12. The process according to claim 11, wherein the coating of the at least one electrode has a thickness of 1.0 mm to 2.0 mm.

13. The process according to claim 7, wherein a graphite member is provided at at least one end of the at least one electrode, and wherein the coating on the outer surface of the at least one electrode does not cover the graphite member.

14. The process according to claim 13, wherein a metal member is provided inside the at least one electrode, the metal member being in contact with the graphite member.

15. The process according to claim 14, wherein the metal component is an iron or carbon steel rod.

16. The process according to claim 7, wherein the coating is covered with a perforated tape or a PTFE mesh or a semi-permeable webbing, which is permeable to the aqueous solution (20) facing the electrode and impermeable to the aqueous solution (20) in the opposite direction.

17. The process according to claim 1, wherein the aqueous solution (20) contains hydrochloric acid at a concentration of 5 to 10%.

18. The process according to claim 1, wherein the pH of the aqueous solution (20) is in the range of 2 to 4.

19. The process according to claim 1, wherein the reaction of reducing the hydrated hydrogen ions to hydrogen gas occurs at a temperature between 20 and 70°C.

20. The process according to claim 19, wherein the reaction of reducing the hydrated hydrogen ions to hydrogen gas occurs at a temperature between 55 and 60°C.

21. The process according to claim 1, wherein the reaction of reducing the hydrated hydrogen ions to hydrogen gas occurs at a pressure below atmospheric pressure.

22. The process according to claim 1, wherein the aqueous solution (20) is regenerated by means of a recycling step and a degassing step, and the degassing step includes a filtration step, wherein oxygen is removed from the aqueous solution (20).

23. The process according to claim 22, wherein a porous baffle membrane filter is used to perform the filtration step, wherein oxygen (O2) and chlorine (Cl2) are released respectively.

24. The process according to claim 23, wherein the porous baffle membrane filter is filled with MnO2.

25. The process according to claim 23, wherein the chlorine thus released is recovered and reintroduced into the aqueous solution (20).

26. The process according to claim 22, wherein the recycling step includes a step of cooling the aqueous solution (20) to maintain a reaction temperature at a substantially constant.

27. An apparatus for producing hydrogen according to any one of claims 1 to 26, the apparatus comprising: at least one buffer tank (1) for storing an aqueous solution (20) comprising hydrochloric acid in a dissociated form; at least one reactor (2, 3) for producing hydrogen, wherein at least one electrode is disposed inside the at least one reactor (2, 3), the at least one electrode being composed of a metal alloy comprising a plurality of metals having different standard reduction potentials; at least one feed line (22, 23) for supplying the aqueous solution (20) from the at least one buffer tank (1) to the at least one reactor (2, 3); and at least one recirculation line (26, 28; 27, 28) for recirculating the aqueous solution (20) from the at least one reactor (2, 3) back to the at least one buffer tank (1). At least one device (10) for regenerating the aqueous solution (20), the at least one device (10) being arranged along the at least one recirculation line (26, 28; 27, 28), and components (4, 5) for extracting hydrogen from the at least one reactor (2, 3).

28. The apparatus according to claim 27, wherein the at least one device (10) comprises a filtration device comprising at least one porous baffle membrane filter capable of separating oxygen (O2) from the aqueous solution (20).

29. The apparatus according to claim 28, wherein the at least one porous baffle membrane filter is filled with MnO2.

30. The apparatus according to claim 28, wherein the filtration device operates under vacuum.

31. The equipment according to claim 27, 28, 29 or 30 includes at least one cooling device (8, 9) along the at least one recirculation line (26, 28; 27, 28).

32. An electrode for use in a process according to any one of claims 1 to 26, the electrode being composed of a metal alloy comprising magnesium and at least one of the following metals: beryllium (Be), aluminum (Al), manganese (Mn), zinc (Zn), iron (Fe), copper (Cu), silicon (Si), and nickel (Ni), wherein the outer surface of the at least one electrode is coated with a coating comprising at least one metal fluoride.

33. The electrode according to claim 32, wherein the metal alloy contains a magnesium content in the range of 85% to 95% by weight.

34. The electrode according to claim 33, wherein the metal alloy contains a magnesium content in the range of 90% to 91% by weight.

35. The electrode according to claim 33, wherein the metal alloy comprises (by weight): A) 90.81% Mg, 5.83% Al, 2.85% Zn, 0.45% Mn, 0.046% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, 0.00050% Ni; or B) 90.65% Mg, 5.92% Al, 2.92% Zn, 0.46% Mn, 0.043% Si, 0.0036% Cu, 0.0012% Be, 0.0010% Fe, 0.00050% Ni.

36. The electrode according to claim 32, 33 or 35, wherein the at least one metal fluoride comprises magnesium fluoride, aluminum fluoride and / or zinc fluoride.

37. The electrode according to claim 36, wherein the coating comprises the at least one metal fluoride mixed with a methacrylic resin.

38. The electrode according to claim 37, wherein the methacrylate resin comprises 50% to 70% (by weight) PFTE, 15% to 25% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 15% to 25% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

39. The electrode according to claim 38, wherein the methacrylate resin comprises 60% (by weight) PFTE, 20% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 20% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

40. The electrode according to claim 36, wherein the coating of the electrode has a thickness of 0.5 mm to 3.0 mm.

41. The electrode according to claim 40, wherein the coating of the electrode has a thickness of 1.0 mm to 2.0 mm.

42. The electrode according to claim 36, wherein a graphite member is provided at one end of the electrode, and wherein the coating on the outer surface of the electrode does not cover the graphite member.

43. The electrode according to claim 42, wherein a metal member is provided inside the electrode, the metal member being in contact with the graphite member.

44. The electrode according to claim 43, wherein the metal component is an iron or carbon steel rod.

45. The electrode according to claim 36, wherein the coating is covered by a perforated tape or a PTFE mesh or a semi-permeable tape, which is permeable to the aqueous solution (20) toward the electrode and impermeable to the aqueous solution (20) in the opposite direction.

46. ​​An aqueous solution (20) for use in a process according to claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or 26, comprising hydrated hydrogen ions (H3O+) and chloride ions (Cl-).

47. A method of coating an electrode comprising a metal alloy containing a plurality of metals having different standard reduction potentials, the electrode being used in a process according to claims 1 to 26, the coating method comprising: - a step of immersing the electrode in a hydrofluoric acid and water bath, wherein the metals constituting the outer surface of the electrode react with the hydrofluoric acid to form a metal fluoride salt of copper fluoride; - a first step of drying the metal fluoride salt of copper fluoride; - a step of applying a methacrylic resin gel onto the copper fluoride; - a second step of drying the mixture thus obtained comprising the metal fluoride and the methacrylic resin.

48. The method of coating an electrode according to claim 47, wherein the methacrylate resin comprises 50% to 70% (by weight) PFTE, 15% to 25% (by weight) 1,2-propanediol monomethacrylate (CAS.27813-02-1) and 15% to 25% (by weight) hydroxyethyl methacrylate (CAS 868-77-9).

49. The method of coating an electrode according to claim 47 or 48, wherein at the end of the second step of drying, the electrode is covered with a perforated tape or a PTFE mesh or a semi-permeable webbing, which is permeable to an aqueous solution (20) toward the electrode but impermeable to the aqueous solution (20) in the opposite direction.

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