|
Prox Dynamics
PROX is an acronym for PReferential OXidation, and refers to the preferential oxidation of a carbon monoxide in a gas mixture by a catalyst. It is intended to remove trace amounts of CO from H2/CO/CO2 mixtures produced by steam reforming and water-gas shift. An ideal PROX catalyst preferentially oxidizes carbon monoxide (CO) using a heterogeneous catalyst placed upon a ceramic support. Catalysts include metals such as platinum, platinum/iron, platinum/ruthenium, gold nanoparticles as well as novel copper oxide/ceramic conglomerate catalysts. Motivation This reaction is a considerable subject area of research with implications for fuel cell design. Its main utility lies in the removal of carbon monoxide (CO) from the fuel cell's feed gas. CO poisons the catalyst of most low-temperature fuel cells. Carbon monoxide is often produced as a by-product from steam reforming of hydrocarbons, which produces hydrogen and CO. It is possible to consume most of the CO by reacting it with stea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate 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. There are two classes of redox reactions: * ''Electron-transfer'' – Only one (usually) electron flows from the reducing agent to the oxidant. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. * ''Atom transfer'' – An atom transfers from one substrate to another. For example, in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with the formation of oxides, other chemical species can serve the same function. In hydrogenation, C=C (and other) bonds ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adsorber
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a fluid (the ''absorbate'') is dissolved by or permeates a liquid or solid (the ''absorbent''). Adsorption is a '' surface phenomenon'', while absorption involves the whole volume of the material, although adsorption does often precede absorption. The term ''sorption'' encompasses both processes, while ''desorption'' is the reverse of it. Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Reaction Engineering
Chemical reaction engineering (reaction engineering or reactor engineering) is a specialty in chemical engineering or industrial chemistry dealing with chemical reactors. Frequently the term relates specifically to catalytic reaction systems where either a homogeneous or heterogeneous catalyst is present in the reactor. Sometimes a reactor ''per se'' is not present by itself, but rather is integrated into a process, for example in reactive separations vessels, retorts, certain fuel cells, and photocatalytic surfaces. The issue of solvent effects on reaction kinetics is also considered as an integral part. Origin of chemical reaction engineering Chemical reaction engineering as a discipline started in the early 1950s under the impulse of researchers at the Shell Amsterdam research center and the university of Delft. The term chemical reaction engineering was apparently coined by J.C. Vlugter while preparing the 1st European Symposium on Chemical Reaction Engineering which was he ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inorganic Reactions
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorganic compounds comprise most of the Earth's crust, although the compositions of the deep mantle remain active areas of investigation. Some simple carbon compounds are often considered inorganic. Examples include the allotropes of carbon (graphite, diamond, buckminsterfullerene, etc.), carbon monoxide, carbon dioxide, carbides, and the following salts of inorganic anions: carbonates, cyanides, cyanates, and thiocyanates. Many of these are normal parts of mostly organic systems, including organisms; describing a chemical as inorganic does not necessarily mean that it does not occur within living things. History Friedrich Wöhler's conversion of ammonium cyanate into urea in 1828 is often cited as the starting point of modern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalysis
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Catalysis is ubiquitous in chemical industry of all kinds. Estimates are that 90% of all commercially produced chemical products involve catalysts at some s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Partial Oxidation
Partial oxidation (POX) is a type of chemical reaction. It occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas which can then be put to further use, for example in a fuel cell. A distinction is made between ''thermal partial oxidation'' (TPOX) and ''catalytic partial oxidation'' (CPOX). Principle Partial oxidation is a technically mature process in which natural gas or a heavy hydrocarbon fuel (heating oil) is mixed with a limited amount of oxygen in an exothermic process. * General reaction: + \frac\mathit -> \mathit + \frac\mathitH2 * Idealized reaction for heating oil: + 6O2 -> + 12H2 * Idealized reaction for coal: + 12O2 -> + 6H2 The formulas given for coal and heating oil show only a typical representative of these complex fuels. Water may be added to lower the combustion temperature and reduce soot formation. Yields are below stoichiometric due to some fuel being fully combusted to carbon dioxide and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Reforming
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: :CH4 + H2O CO + 3 H2 The reaction is strongly endothermic (Δ''H''SR = 206 kJ/mol). Hydrogen produced by steam reforming is termed 'grey hydrogen' when the waste carbon monoxide is released to the atmosphere and 'blue hydrogen' when the carbon monoxide is (mostly) captured and stored geologically - see carbon capture and storage. Zero carbon 'green' hydrogen is produced by thermochemical water splitting, using solar thermal, low- or zero-carbon electricity or waste heat, or electrolysis, using low- or zero-carbon electricity. Zero carbon emissions 'turquoise' hydrogen is produced by one-step methane pyrolysis of natural gas. Steam reforming of natural gas produces most of the world ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanol Reformer
A methanol reformer is a device used in chemical engineering, especially in the area of fuel cell technology, which can produce pure hydrogen gas and carbon dioxide by reacting a methanol and water (steam) mixture. :\mathrm \Delta H_^0 = 49.2\ \mathrm Methanol is transformed into hydrogen and carbon dioxide by pressure and heat and interaction with a catalyst. Technology A mixture of water and methanol with a molar concentration ratio (water:methanol) of 1.0 - 1.5 is pressurized to approximately 20 bar, vaporized and heated to a temperature of 250 - 360 °C. The hydrogen that is created is separated through the use of Pressure swing adsorption or a hydrogen-permeable membrane made of polymer or a palladium alloy. There are two basic methods of conducting this process. * The water-methanol mixture is introduced into a tube-shaped reactor where it makes contact with the catalyst. Hydrogen is then separated from the other reactants and products in a l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haber Process
The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and Carl Bosch, who developed it in the first decade of the 20th century. The process converts atmospheric nitrogen (N2) to ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst under high temperatures and pressures: : \ce \quad \Delta H^\circ = -91.8~\text Though this reaction is exothermic (i.e. it releases energy, albeit not very much), it results in a decrease in entropy, which is the central reason why it is very challenging to carry out. Before the development of the Haber process, it had been difficult to produce ammonia on an industrial scale, with early methods, such as the Birkeland–Eyde process and the Frank–Caro process, all highly inefficient. During World War I, the Haber process provided Germany with a so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Methanation
Methanation is the conversion of carbon monoxide and carbon dioxide (COx) to methane (CH4) through hydrogenation. The methanation reactions of COx were first discovered by Sabatier and Senderens in 1902. CO''x'' methanation has many practical applications. It is a means of carbon oxide removal from process gases and is also being discussed as an alternative to PROX in fuel processors for mobile fuel cell applications. Methanation as a means of producing synthetic natural gas has been considered since the 1970s. More recently it has been considered as a way to store energy produced from solar or wind power using power-to-gas systems in conjunction with existing natural gas storage. Chemical reactions The following reactions describe the methanation of carbon monoxide and carbon dioxide respectively: :CO + 3H2 -> CH4 + H2O -206 kJ/mol :CO2 + 4H2 -> CH4 + 2 H2O -164 kJ/mol The methanation reactions are classified as exothermic and their energy of formations are listed. There is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term ''exothermic'' was first coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). Two types of chemical reactions Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: Exothermic After an exothermic reaction, more energy has been released to the surroundings than was absorbed to initiate and maintain the reaction. An example would be the burn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quickly, very small amounts of catalyst often suffice; mixing, surface area, and temperature are important factors in reaction rate. Catalysts generally react with one or more reactants to form intermediates that subsequently give the final reaction product, in the process of regenerating the catalyst. Catalysis may be classified as either homogeneous, whose components are dispersed in the same phase (usually gaseous or liquid) as the reactant, or heterogeneous, whose components are not in the same phase. Enzymes and other biocatalysts are often considered as a third category. Catalysis is ubiquitous in chemical industry of all kinds. Estimates are that 90% of all commercially produced chemical products involve catalysts at some s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
