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The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia. It converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a finely divided iron metal catalyst:
Redox is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction.
Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principally used for producing ammonia or methanol. Syngas is combustible and can be used as a fuel. Historically, it has been used as a replacement for gasoline, when gasoline supply has been limited; for example, wood gas was used to power cars in Europe during WWII.
Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.
Wüstite is a mineral form of mostly iron(II) oxide found with meteorites and native iron. It has a grey colour with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound.
High-temperature electrolysis is a technology for producing hydrogen from water at high temperatures or other products, such as iron or carbon nanomaterials, as higher energy lowers needed electricity to split molecules and opens up new, potentially better electrolytes like molten salts or hydroxides. Unlike electrolysis at room temperature, HTE operates at elevated temperature ranges depending on the thermal capacity of the material. Because of the detrimental effects of burning fossil fuels on humans and the environment, HTE has become a necessary alternative and efficient method by which hydrogen can be prepared on a large scale and used as fuel. The vision of HTE is to move towards decarbonization in all economic sectors. The material requirements for this process are: the heat source, the electrodes, the electrolyte, the electrolyzer membrane, and the source of electricity.
Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment (see: Mars Black). For this purpose, it is synthesized rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production.
Steam reforming or steam methane reforming (SMR) is a method for producing syngas (hydrogen and carbon monoxide) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen production. The reaction is represented by this equilibrium:
The water–gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen:
Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore into iron by a reducing gas which contains elemental carbon and/or hydrogen. When hydrogen is used as the reducing gas no carbon dioxide is produced. Many ores are suitable for direct reduction.
Hydrogen gas is produced by several industrial methods. Nearly all of the world's current supply of hydrogen is created from fossil fuels. Most hydrogen is gray hydrogen made through steam methane reforming. In this process, hydrogen is produced from a chemical reaction between steam and methane, the main component of natural gas. Producing one tonne of hydrogen through this process emits 6.6–9.3 tonnes of carbon dioxide. When carbon capture and storage is used to remove a large fraction of these emissions, the product is known as blue hydrogen.
In geology, a redox buffer is an assemblage of minerals or compounds that constrains oxygen fugacity as a function of temperature. Knowledge of the redox conditions (or equivalently, oxygen fugacities) at which a rock forms and evolves can be important for interpreting the rock history. Iron, sulfur, and manganese are three of the relatively abundant elements in the Earth's crust that occur in more than one oxidation state. For instance, iron, the fourth most abundant element in the crust, exists as native iron, ferrous iron (Fe2+), and ferric iron (Fe3+). The redox state of a rock affects the relative proportions of the oxidation states of these elements and hence may determine both the minerals present and their compositions. If a rock contains pure minerals that constitute a redox buffer, then the oxygen fugacity of equilibration is defined by one of the curves in the accompanying fugacity-temperature diagram.
Chemical looping combustion (CLC) is a technological process typically employing a dual fluidized bed system. CLC operated with an interconnected moving bed with a fluidized bed system, has also been employed as a technology process. In CLC, a metal oxide is employed as a bed material providing the oxygen for combustion in the fuel reactor. The reduced metal is then transferred to the second bed and re-oxidized before being reintroduced back to the fuel reactor completing the loop. Fig 1 shows a simplified diagram of the CLC process. Fig 2 shows an example of a dual fluidized bed circulating reactor system and a moving bed-fluidized bed circulating reactor system.
The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few.
Anaerobic corrosion is a form of metal corrosion occurring in anoxic water. Typically following aerobic corrosion, anaerobic corrosion involves a redox reaction that reduces hydrogen ions and oxidizes a solid metal. This process can occur in either abiotic conditions through a thermodynamically spontaneous reaction or biotic conditions through a process known as bacterial anaerobic corrosion. Along with other forms of corrosion, anaerobic corrosion is significant when considering the safe, permanent storage of chemical waste.
For chemical reactions, the iron oxide cycle (Fe3O4/FeO) is the original two-step thermochemical cycle proposed for use for hydrogen production. It is based on the reduction and subsequent oxidation of iron ions, particularly the reduction and oxidation between Fe3+ and Fe2+. The ferrites, or iron oxide, begins in the form of a spinel and depending on the reaction conditions, dopant metals and support material forms either Wüstites or different spinels.
Thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled.
The Schikorr reaction formally describes the conversion of the iron(II) hydroxide (Fe(OH)2) into iron(II,III) oxide (Fe3O4). This transformation reaction was first studied by Gerhard Schikorr. The global reaction follows:
Chemical looping reforming (CLR) and gasification (CLG) are the operations that involve the use of gaseous carbonaceous feedstock and solid carbonaceous feedstock, respectively, in their conversion to syngas in the chemical looping scheme. The typical gaseous carbonaceous feedstocks used are natural gas and reducing tail gas, while the typical solid carbonaceous feedstocks used are coal and biomass. The feedstocks are partially oxidized to generate syngas using metal oxide oxygen carriers as the oxidant. The reduced metal oxide is then oxidized in the regeneration step using air. The syngas is an important intermediate for generation of such diverse products as electricity, chemicals, hydrogen, and liquid fuels.
Magnetic roasting technology refers to the process of heating materials or ores under specific atmospheric conditions to induce chemical reactions. This process selectively converts weakly magnetic iron minerals such as hematite (Fe2O3), siderite (FeCO3), and limonite (Fe2O3·nH2O) into strongly magnetic magnetite (Fe3O4) or maghemite (γ-Fe2O3), while the magnetic properties of gangue minerals remain almost unchanged.
References
- ↑ Sponge iron process for manned space exploration
- ↑ A novel process for stationary hydrogen production: the reformer sponge iron cycle
- ↑ Kindermann, H.; Kornberger, M.; Hierzer, J.; Besenhard, J. O.; Hacker, V. (18 August 2005). "First investigations of structural changes of the contact mass in the RESC process for hydrogen production". Journal of Power Sources. Selected papers presented at the Fuel Cells Science and Technology Meeting. 145 (2): 697–701. Bibcode:2005JPS...145..697K. doi:10.1016/j.jpowsour.2004.12.074.