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Microreactor
A microreactor or microstructured reactor or microchannel reactor is a device in which chemical reactions take place in a confinement with typical lateral dimensions below 1 mm; the most typical form of such confinement are microchannels. Microreactors are studied in the field of micro process engineering, together with other devices (such as micro heat exchangers) in which physical processes occur. The microreactor is usually a continuous flow reactor (contrast with/to a batch reactor). Microreactors can offer many advantages over conventional scale reactors, including improvements in energy efficiency, reaction speed and yield, safety, reliability, scalability, on-site/on-demand production, and a much finer degree of process control. History Gas-phase microreactors have a long history but those involving liquids started to appear in the late 1990s. One of the first microreactors with embedded high performance heat exchangers were made in the early 1990s by the Central ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuous Flow Reactor
In flow chemistry, also called reactor engineering, a chemical reaction is run in a continuously flowing stream rather than in batch production. In other words, pumps move fluid into a reactor, and where tubes join one another, the fluids contact one another. If these fluids are reactive, a reaction takes place. Flow chemistry is a well-established technique for use at a large scale when manufacturing large quantities of a given material. However, the term has only been coined recently for its application on a laboratory scale by chemists and describes small pilot plants, and lab-scale continuous plants. Often, microreactors are used. Batch vs. flow Comparing parameter definitions in Batch vs Flow *Reaction stoichiometry: In batch production this is defined by the concentration of chemical reagents and their volumetric ratio. In flow this is defined by the concentration of reagents and the ratio of their flow rate. *Residence time: In batch production this is determined by ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Micro Process Engineering
{{Unreferenced, date=June 2019, bot=noref (GreenC bot) Micro process engineering is the science of conducting chemical or physical processes (unit operations) inside small volumina, typically inside channels with diameters of less than 1 mm (microchannels) or other structures with sub-millimeter dimensions. These processes are usually carried out in continuous flow mode, as opposed to batch production, allowing a throughput high enough to make micro process engineering a tool for chemical production. Micro process engineering is therefore not to be confused with microchemistry, which deals with very small overall quantities of matter. The subfield of micro process engineering that deals with chemical reactions, carried out in microstructured reactors or "microreactors", is also known as microreaction technology. The unique advantages of microstructured reactors or ''microreactors'' are enhanced heat transfer due to the large surface area-to-volume ratio, and enhanced mass t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Work-up (chemistry)
In chemistry, work-up refers to the series of manipulations required to isolate and purify the product(s) of a chemical reaction. The term is used colloquially to refer to these manipulations, which may include: * deactivating any unreacted reagents by quenching a reaction. * cooling the reaction mixture or adding an '' antisolvent'' to induce precipitation, and collecting or removing the solids by filtration, decantation, or centrifugation. * changing the protonation state of the products or impurities by adding an acid or base. * separating the reaction mixture into organic and aqueous layers by liquid-liquid extraction. * removal of solvents by evaporation. * purification by chromatography, distillation or recrystallization. The work-up steps required for a given chemical reaction may require one or more of these manipulations. Work-up steps are not always explicitly shown in reaction schemes. Written experimental procedures will describe work-up steps but will usually ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nitration
In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group () into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters () between Alcohol (chemistry), alcohols and nitric acid (as occurs in the Organic synthesis, synthesis of nitroglycerin). The difference between the resulting molecular structures of nitro compounds and nitrates () is that the nitrogen atom in nitro compounds is directly Chemical bond, bonded to a non-oxygen atom (typically carbon or another nitrogen atom), whereas in nitrate esters (also called organic nitrates), the nitrogen is bonded to an oxygen atom that in turn usually is bonded to a carbon atom (nitrito group). There are many major industrial applications of nitration in the strict sense; the most important by volume are for the production of nitroaromatic compounds such as nitrobenzene. The technology is long-standing and mature. : Nitration rea ... [...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 An exothermic reaction occurs when heat is released to the surroundings. According to the IUPAC, an exothermic reaction is "a reaction for which the overall stand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Kinetics
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate. Chemical kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition states, as well as the construction of mathematical models that also can describe the characteristics of a chemical reaction. History The pioneering work of chemical kinetics was done by German chemist Ludwig Wilhelmy in 1850. He experimentally studied the rate of inversion of sucrose and he used integrated rate law for the determination of the reaction kinetics of this reaction. His work was noticed 34 years later by Wilhelm Ostwald. In 1864, Peter Waage and Cato Guldberg published the law ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating Temperature
An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature (or peak operating temperature). Outside this range of safe operating temperatures the device may fail. It is one component of reliability engineering. Similarly, biological systems have a viable temperature range, which might be referred to as an "operating temperature". Ranges Most semiconductor devices are manufactured in several temperature grades. Broadly accepted grades are: *Commercial: 0 °C to 70 °C () *Industrial: −40 °C to 85 °C () *Military: −55 °C to 125 °C () Nevertheless, each manufacturer defines its own temperature grades so designers must pay attention to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs. A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage of an overall chemical reaction. The detailed steps of a reaction are not observable in most cases. The conjectured mechanism is chosen because it is thermodynamically feasible and has experimental support in isolated intermediates (see next section) or other quantitative and qualitative characteristics of the reaction. It also describes each reactive intermediate, activated complex, and transition state, which bonds are broken (and in what order), and which bonds are formed (and in what order). A complete mechanism must also explain the reason for the reactants and catalyst used, the stereochemistry observed in reactants and products, all products formed and the amount of each. The electron or arrow pushing method is often used in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a substance ''consumed'' in the course of a chemical reaction. ''Solvents'', though involved in the reaction mechanism, are usually not called reactants. Similarly, ''catalysts'' are not consumed by the reaction, so they are not reactants. In biochemistry, especially in connection with enzyme-catalyzed reactions, the reactants are commonly called substrates. Definitions Organic chemistry In organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include the Collins reagent, Fenton's reagent, and Grignard reagents. Analytical chemistry In analytical chemistry, a reag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Transfer Coefficient
In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the Proportional (mathematics), proportionality constant between the heat flux and the thermodynamic driving force for the Heat transfer, flow of heat (i.e., the Temperature gradient, temperature difference, ). It is used to calculate heat transfer between components of a system; such as by convection between a fluid and a solid. The heat transfer coefficient has SI units in Watt, watts per square meter per kelvin (W/(m2K)). The overall heat transfer rate for combined modes is usually expressed in terms of an overall Thermal conduction, conductance or heat transfer coefficient, . Upon reaching a steady state of flow, the heat transfer rate is: :\dot=hA(T_2-T_1) where (in SI units): : \dot: Heat transfer rate (W) : h: Heat transfer coefficient (W/m2K) : A: surface area where the heat transfer takes place (m2) : T_2: temperature of the surrounding fluid (K) : T_1: temperature of the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
