Exothermic process

Résumé

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

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https://en.wikipedia.org/wiki/Exothermic_process

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In the context of a semester project conducted at the LENI Lab at EPFL, a study on reactors integration and the effect of the operating conditions of the reactor and the reaction, on the T-H profile was carried out with the help of an Exergy Analysis. At the end, a real temperature enthalpy profile inside the reactor was drawn and analyzed and finally a recommendation was proposed on a systematic decrease in reaction’s operating temperature, which gave a gain in exergy delivered for the exothermic reaction used in this project.

2013

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Micro-batch reactor for catching intermediates and monitoring kinetics of rapid and exothermic homogeneous reactions

Olivier Détraz, Madhvanand Namadeo Kashid, Lioubov Kiwi, Petra Prechtl, Albert Renken, Mireia Santacana Moya

The mechanism and kinetics of rapid and exothermic reactions is difficult to study using conventional offline techniques. This paper deals with experimental investigations of highly exothermic and fast model reaction (cyclisation of pseudoionone) using slug flow (micro-batches) microstructured reactor (MSR). The slug flow was obtained using a cross-junction and identifying suitable inert carrier fluid (perfluorohexane) immiscible with the species participating in the reaction. MSR provided short reaction time in a continuous slug-flow that allowed catching intermediates and monitoring the kinetics. The small reaction volumes suppress the temperature rise by removing the reaction heat. The kinetics has been studied under isothermal conditions and more reliable reaction network has been proposed. Finally, the mixing within the slugs and its influence on the obtained results was accessed. This methodology has a generic nature and can be applied for a wide variety of fast exothermic homogeneous reactions. (C) 2012 Elsevier B.V. All rights reserved.

Elsevier2013

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Carbon nanofibers grown on metallic filters as novel catalytic materials

Lioubov Kiwi, Pascal Tribolet

Carbon nanofibers (CNF) were synthesized on sintered metal fibers (SMF) filters of nickel and Ni-containing alloys (Inconel, stainless steel (SS)) by thermal chemical vapor deposition of ethane in the presence of hydrogen at not, vert, similar660 °C. The CNFs were formed directly over the SMF filters without deposition of metal particles. The catalytic active sites leading to the CNF formation were attained by oxidation–reduction of the SMF filter. The CNFs present platelet morphology as determined by X-ray diffraction and transmission electron microscopy. The CNF/SMF composites have thin carbon layer in the microns range strongly anchored to the metal surface. The initial open structure of SMF filters is preserved. Scanning electron microscopy together with temperature programmed oxidation suggests the formation of uniform CNFs deposits on SMFInconel with fiber's diameters in the range of 70 nm. Carbon deposits with a different nature were observed over SMFNi and SMFss. The CNF/SMFInconel composites have high specific surface area due to mesopores of CNFs, high thermo-conductivity and open 3D macrostructure. This is advantageous for catalytic applications, especially during the catalysis of highly exo/endothermic reactions in reactors with structured catalytic bed.

2005

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