A method for producing hydrogen and magnetite from water and iron.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KS IPR UG
- Filing Date
- 2024-06-12
- Publication Date
- 2026-07-06
AI Technical Summary
Conventional hydrogen production methods, such as electrolysis and steam-iron reaction, are energy-intensive and pose safety risks due to gas-phase reactions, while using iron and acid is uneconomical and generates waste, necessitating a safer and more energy-efficient process for hydrogen production.
A method involving the reaction of liquid water with iron in the presence of an iron(II) salt catalyst at controlled temperatures and pressures, primarily in the liquid phase, producing hydrogen and magnetite, which can be reused for further hydrogen production.
This method enhances energy efficiency, reduces safety risks, and enables efficient hydrogen storage and transportation by using recovered iron, eliminating the need for cryogenic liquefaction and reducing waste generation.
Smart Images
Figure 2026522129000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for producing hydrogen and magnetite from water and iron, in which water reacts with iron in the presence of a catalyst. The iron used can be obtained beforehand, for example, by reduction of formed magnetite or other compounds.
Background Art
[0002] Hydrogen is being considered as a future energy carrier. It is an energy source with high versatility and easy transportability. One of the hydrogen production methods is electrolysis of water. However, this process requires a large amount of energy and also requires a lot of energy for storage. To improve storage, hydrogen is cooled to -253°C under extremely high pressure. This has the advantage of liquefying the gas and enabling more compact transport. However, this compression process consumes an enormous amount of energy.
[0003] The steam-iron reaction for hydrogen production has been known for over 100 years and was industrially utilized until the early 1970s. The steam-iron reaction is usually carried out at atmospheric pressure around 500°C. Since water evaporates in this process, the reaction occurs in the gas phase. As a result, energy efficiency is low because it is necessary to evaporate water, and high safety standards are required for the reaction and the process due to the gas phase.
[0004] Furthermore, it is generally known that hydrogen can be produced using iron and an acid. However, this requires 1 equivalent of iron and 2 equivalents of acid for every 1 equivalent of hydrogen produced. This is a very uneconomical method for hydrogen production, and since stoichiometric amounts of waste are generated, this process is usually not used outside the laboratory scale.
Summary of the Invention
Problems to be Solved by the Invention
[0005] Given the problems and shortcomings of conventional technologies, as well as the challenges surrounding fossil fuels and climate change, there is a strong need for a new process to produce hydrogen from iron in a safe and energy-efficient manner. Furthermore, an appropriate energy storage system is also necessary to enable the simple and efficient transportation of hydrogen in the future. [Means for solving the problem]
[0006] Remarkably, it has been shown that hydrogen can be produced from liquid water by using a combination of iron and an iron(II) salt catalyst. Using liquid water minimizes safety risks and reduces the energy required for water evaporation. Furthermore, the produced hydrogen can be used to reduce iron, and the recovered iron can be reused in subsequent processes to produce more hydrogen. Therefore, this process offers new possibilities for long-term indirect hydrogen storage using recovered iron. As a result, hydrogen can be transported and stored more energy-efficiently and safely. [Modes for carrying out the invention]
[0007] Therefore, in the first embodiment, the object of the present invention is a method for producing hydrogen and magnetite from water and iron, wherein water is in contact with iron in the presence of at least one catalyst as a liquid, a) The at least one catalyst is selected from iron(II) chloride, iron(II) sulfate, iron(II) nitrate, iron(II) phosphate, or iron(II) acetate. b) The procedure is carried out at a temperature of 60-400°C. c) It is carried out under pressure where water is primarily in liquid form. This is achieved by a method characterized by the following features.
[0008] Therefore, according to the present invention, iron and water are brought into contact, particularly at a temperature of 90 to 190°C, in the presence of an iron(II) catalyst selected from iron(II) chloride, iron(II) sulfate, iron(II) nitrate, iron(II) phosphate, or iron(II) acetate. Furthermore, the pressure in the method according to the present invention is selected so that water exists primarily as a liquid. According to the present invention, this means that in the reactor where the reaction takes place, a gas phase may exist above the liquid phase, including water in vapor form. However, according to the present invention, iron reacts only with water in the liquid phase. Also according to the present invention, it is not important which components are supplied first and which are added later. Iron and water react with each other in an aqueous solution, and the iron is oxidized to iron oxide or magnetite. Hydrogen is produced. According to the present invention, "primarily liquid" preferably means that at least 85% by weight, particularly at least 90% by weight, and especially at least 95% by weight of water relative to the total amount of water is present in the liquid phase.
[0009] Therefore, the method according to the present invention provides a novel and energy-efficient method for hydrogen production. The hydrogen is then recovered and can be used directly as a raw material or energy carrier. In a preferred embodiment, the generated magnetite can be reacted with hydrogen again in a subsequent process, thereby producing iron. This iron can be repeatedly used to produce hydrogen using the process of the present invention, thus functioning as an indirect energy carrier for hydrogen. This aspect solves the problem of having to cool hydrogen to -253°C for storage as a liquid. Furthermore, all the risks associated with transporting liquid hydrogen are eliminated.
[0010] According to the present invention, magnetite is a mineral belonging to the mineral class of oxides and hydroxides, and is the most stable compound of iron and oxygen. Its exact chemical name is iron(II,III) oxide. Other iron oxides can also be produced by the method according to the present invention. In the process according to the present invention, iron(II) oxide is first produced, which is immediately further decomposed into magnetite. This decomposition also produces elemental iron, which reacts with the help of an iron(II) salt catalyst selected from iron(II) chloride, iron(II) sulfate, iron(II) nitrate, iron(II) phosphate, or iron(II) acetate to form iron oxide and hydrogen.
[0011] A key advantage of the method according to the present invention is the use of liquid water, which requires far less energy than a water vapor-gas phase reaction. To ensure this, the pressure must be selected to be less than the vapor pressure of water. Those skilled in the art will understand what pressure is appropriate for carrying out this method using liquid water. Thus, the method according to the present invention carried out at a temperature of 100°C requires a pressure of at least approximately 1013 hPa or 1 bar, while the method according to the present invention carried out at, for example, 160°C requires a pressure of at least approximately 6200 hPa or 6.2 bar. Further vapor pressures corresponding to the method according to the present invention can be found in the prior art.
[0012] The catalyst according to the present invention increases the reaction rate by reducing the reaction enthalpy required for the reaction between water and iron. This catalyst is not consumed and can be used multiple times. According to the present invention, the catalyst comprises an iron(II) salt selected from iron(II) chloride, iron(II) sulfate, iron(II) nitrate, iron(II) phosphate, or iron(II) acetate. Other possible iron salts are known to those skilled in the art and can also be used in the method according to the present invention. An important aspect of the catalyst according to the present invention is that the number of catalyst turnovers does not change after at least 10, preferably 15, and most preferably 20 processes according to the present invention, and therefore the conversion rates of iron and water are maintained at the same reaction time. Surprisingly, catalyst tests have shown that iron(III) salts cannot be used in the method according to the present invention because no reaction occurs.
[0013] In the method according to the present invention, the reaction temperature also depends on the catalyst used. In a preferred embodiment, since the decomposition temperature of iron(II) acetate is 190°C, the temperature is selected from the range of 90°C to 190°C. Therefore, in another preferred embodiment, other catalysts can enable higher temperatures in the method according to the present invention. In this case, the temperature of the method is determined by the decomposition temperature of the iron catalyst used. Therefore, in the method according to the present invention, a temperature between 60°C and 400°C is selected, preferably between 80°C and 200°C, and most preferably between 90°C and 190°C.
[0014] Furthermore, the method according to the present invention can be carried out at temperatures below the critical point of water. In preferred embodiments, temperatures between 0°C and 374°C are selected. In other preferred embodiments, temperatures of 100°C to 350°C, 80°C to 250°C, 150°C to 320°C, or 200°C to 300°C are possible, provided that the pressure is selected such that the water is primarily in a liquid state.
[0015] In preferred embodiments, the catalyst is used in the method according to the present invention in an amount of 1 to 100 mol%, preferably 5 to 100 mol%,. The amount of catalyst refers to the limiting reactant or limiting reagent in this method. This may be either the amount of iron or the amount of water, depending on the requirements. It should be understood that, according to the present invention, mol% refers to the ratio of the limiting reagent to the catalyst. Therefore, in the case of 1 mole of catalyst and 100 moles of limiting reagent, the amount of catalyst or catalyst loading is 1 mol%. Thus, it should be understood that the limiting reagent is the reactant used in the method according to the present invention, and in this context, the terms reagent and reactant are interchangeable.
[0016] Furthermore, the method according to the present invention allows for pressure adjustment according to temperature. In a preferred embodiment of this method, the pressure can be up to 221 bar, 30 bar, or 15 bar. Those skilled in the art will understand what pressure is appropriate to keep below the vapor pressure of water.
[0017] Therefore, in a preferred embodiment, the method according to the present invention can be carried out at higher pressures and temperatures, particularly below the critical point at which water remains liquid, with a pressure below 221 bar and a temperature up to 374°C.
[0018] In a further preferred embodiment of the method according to the present invention, the method may include a further step d) for separating magnetite and hydrogen from the reaction solution at the end of the reaction. Furthermore, in a preferred embodiment, the magnetite and catalyst can be separated from each other so that the catalyst can be reused in the process of the present invention. Separation of magnetite and catalyst can be carried out, for example, using a magnet and / or a filter.
[0019] Furthermore, according to the present invention, in preferred embodiments, magnetite can be separated from the catalyst by washing with a solvent. Suitable solvents are known to those skilled in the art. These are selected depending on the type of catalyst. Preferred solvents are polar organic solvents and / or water. Most commonly preferred solvents for separating the catalyst are, for example, 1,4-dioxane, dichloromethane, ethyl acetate, and / or mixtures thereof.
[0020] In a further preferred embodiment, additional catalyst species may be added to the method according to the present invention to increase or decrease the reaction rate or reaction enthalpy, respectively. Preferred catalysts that can be added are metal oxides, such as titanium oxide, magnesium oxide, and / or zinc oxide. Other transition metals or metal oxides may also be used.
[0021] More preferably, this method is a continuous process in which iron and water are continuously introduced into a container to obtain hydrogen and magnetite.
[0022] Therefore, in the present invention, the reaction is carried out in the liquid phase of water at 60°C to 400°C, preferably 90°C to 190°C, and under a pressure exceeding the vapor pressure of water, without the presence of oxygen. Advantages include a smaller, simpler, and more compact design, lower energy loss / higher energy efficiency (lower temperature and no water evaporation), no passivation of the iron surface, and a higher and faster conversion rate. More preferably, the reaction is carried out in a sealed container so that thermal energy and pressure can be maintained while reactants are supplied and products are removed. Removal or separation is carried out as described in the preceding paragraph.
[0023] In a more preferred embodiment, the method is carried out in a gas phase that excludes oxygen. In this embodiment, the method is carried out under an inert gas, preferably nitrogen or a noble gas, preferably argon. It is also possible to carry out the method according to the present invention in the absence of CO2, if preferred.
[0024] Furthermore, in a preferred embodiment, the separated magnetite can be reduced again in a subsequent process in order to utilize the obtained iron as an indirect hydrogen source.
Industrial Applicability
[0025] The method according to the present invention can also be used for storing renewable energy for the purpose of converting excess wind or solar energy into hydrogen and storing it. However, preferably, the storage is carried out using the magnetite or iron produced by this method. In this case, the energy is converted into hydrogen, for example by electrolysis, and used to reduce magnetite or other iron compounds. As a result, the obtained iron can be converted back into hydrogen and magnetite again in the method according to the present invention. Therefore, the obtained iron can be regarded as an indirect hydrogen or energy storage medium. The method according to the present invention is not carried out in the presence of oxygen because the use of oxygen causes deterioration of the catalyst. The catalyst is converted into iron(III) acetate by oxygen and becomes unusable during the process.
Brief Description of Drawings
[0026] [Figure 1] It is a diagram schematically showing a sealed apparatus in which the method according to the present invention is carried out.
Claims
1. A method for producing hydrogen and magnetite from water and iron, wherein the water in liquid form comes into contact with the iron in the presence of at least one catalyst, a) The at least one catalyst is selected from iron(II) chloride, iron(II) sulfate, iron(II) nitrate, iron(II) phosphate, or iron(II) acetate, b) The process is carried out at a temperature of 60°C to 400°C. c) The water is carried out under pressure, where it is mainly in liquid form. A method characterized by the following features.
2. The method according to claim 1, characterized in that the catalyst is used in an amount of 1 to 100 mol%, preferably 5 to 100 mol%, relative to the limiting reagent.
3. The method according to at least one of claim 1 or 2, characterized in that it is carried out at a higher pressure and a corresponding temperature, in particular at a pressure below 221 bar and a temperature up to 373°C, such that the water remains in liquid.
4. d) A step of separating magnetite and hydrogen from the reaction solution at the end of the reaction. The method according to at least one of claims 1 to 3, further comprising:
5. The method according to at least one of claims 1 to 4, characterized in that the magnetite and the catalyst are separated from each other, and the catalyst can be reused in the method according to at least one of claims 1 to 4.
6. The method according to claim 5, characterized in that the separation of the magnetite and the catalyst is carried out by using a magnet, washing, and / or using a filter.
7. The method according to at least one of claims 1 to 6, characterized in that at least one further catalyst selected from metal oxides, particularly titanium oxide, is used.
8. The method according to claim 1, characterized in that it is carried out in the absence of oxygen, preferably in the presence of an inert gas.
9. The method according to at least one of claims 1 to 8, characterized in that it is carried out at a temperature of 90°C to 190°C.
10. The method according to at least one of claims 1 to 9, characterized in that the obtained iron is used for indirect hydrogen storage.