Letteratura scientifica selezionata sul tema "Alcool (combustible) – Propriétés physico-chimiques"
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Tesi sul tema "Alcool (combustible) – Propriétés physico-chimiques"
Pelé, Ronan. "Potentiel de l'ammoniac comme additif à l'éthanol pour les moteurs à allumage commandé". Electronic Thesis or Diss., Orléans, 2023. http://www.theses.fr/2023ORLE1035.
Testo completoDecarbonization of all forms of energy is urgent to mitigate climate change. Ammonia produced from renewable energies is not only an energy vector but also a potential carbon-free fuel in its structure for all thermal applications (gas turbine, ovens, and engines). Its less reactive combustion than traditional fuels can be improved with the addition of a more reactive and carbon neutral fuel, such as hydrogen, and biofuels, such as bio-ethanol. The objective of this thesis work is therefore to evaluate the potential of ammonia/ethanol mixtures from the injection and combustion process to the efficiency and pollutant emitted in the case of a spark ignition engine. A first part is devoted to the thermodynamics of mixtures of ammonia and ethanol. It has been shown that these two molecules, which are completely miscible with each other, can be injected in liquid form and mixed in the combustion chamber. The characterization of the liquid spray, in the second part, made it possible to highlight their radically different morphology from sprays of pure ethanol, and of gasoline as a reference. The strong vaporization of ammonia causes a very strong drop in temperature (down to -40/-60°C) which makes the spray thinner and longer. This very different geometry affects the local air/fuel mixture in the combustion chamber, affecting the process of initiation and development of combustion and the formation of pollutants. Laminar flame speed is one of the key fundamental parameters for thermal applications and simulations. It was characterized in a third part for the different mixtures. A small addition of ethanol greatly improves combustion, comparisons with current kinetic mechanisms have also been carried out in order to show the various research still necessary. The last part was devoted to the engine application: good performance and stability of these mixtures was obtained, making these mixtures good candidates for decarbonizing transport and electricity production by generator. Measurements of exhaust pollutant emissions have shown that adding ethanol to ammonia makes it possible to limit the release of unburned ammonia as well as N2O, a gas with a strong impact on global warming. However, NOx and CO emissions do not evolve monotonically with the addition of ethanol and a maximum was obtained around 50/50, showing the limit of these mixtures
Lefèvre, Gauthier. "Propriétés physico-chimiques de nouveaux matériaux en couches minces pour le stockage d'hydrogène". Thesis, Artois, 2018. http://www.theses.fr/2018ARTO0406.
Testo completoHydrogen storage is probably the last lock facing the development of fuel cells system.Hydrogen is a non-harmful, non-polluting that can be used as an energy vector, allowing to produce fossil fuel free electricity efficiently and releasing only water.It could trigger the next technological and green revolution, marking the end of environmental concerns related to energy.Hydrogen is the most energetic gas. These double-edged caracteristics makes it attractive and unsafe at the same time. Solid state storage can be seen as a solution in spite of a moderate hydrogen uptake and a poor desorption process.In this context, research of new materials with enhanced physico-chemical properties is desirable and represent the aim of this work.This thesis is an investigation study. On the one hand, with the help of efficient theoretical structural prediction systems, an exploration of the infinite possibilities offered by metal alloys has been performed. On the other hand, pulsed laser deposition of metal thin films has been implemented to make use of its benefits.The present theoretical study has highlighted the influence of external strains on stability and emergence of alloys in numerous binary systems. In addition, a search for potential hydrides was carried out. Informations obtained are encouraging the use of similar prediction schemes in order to identify new systems.From metallic thin films made by pulsed laser ablation, deposition difficulties and disparities in procedures have been put forward. Nonetheless, singular morphologies have been achieved by this process, opening new insights for designing novel materials
Saravia, Alvaro. "Synthèse des combustibles carbures à partir de précurseurs nanostructurés : impact sur la carboréduction et les propriétés physico-chimiques". Thesis, Montpellier, Ecole nationale supérieure de chimie, 2015. http://www.theses.fr/2015ENCM0009.
Testo completoThe synthetic route conventionally used to manufacture carbides fuels involves carboreduction of a mixture of AnO2 powders and graphite at high temperature (1600 °C) and under a low vacuum. These conditions are disadvantageous for the synthesis of mixed carbides (U,Pu)C due to volatilization of plutonium. This is why one of the main goals of this work was to reduce the temperature of carboreduction. Our work was mainly carried on the lowering of the temperature of carboreduction of uranium oxide. This result was achieved by increasing the reaction surface between the carbon and uranium oxide. To do this colloidal suspensions of uranium oxide nanoparticles were prepared and stabilized with cellulose ethers. Cellulose ethers serve both as a stabilizer for the uranium oxide nanoparticles, but also as a carbon source for the carboreduction. These precursors have shown to be more efficient for the carboreduction compared to the standard precursors: a reduction of 300 °C on the carboreduction temperature was obtained under low vacuum. The impact of this type of precursors on the carboreduction and physicochemical properties and the structural and microstructural characterization of obtained carbide were performed
Chaabane-Dammak, Lobna. "Étude des propriétés physico-chimiques et de la microstructure des membranes échangeuses d’ions, modifiées ou non, en présence d’un solvant mixte eau-méthanol et à différentes températures". Paris 12, 2007. http://www.theses.fr/2007PA120084.
Testo completoWe have carried out a systematic study of the static and dynamic characteristics of two commercial MEC (CM2 and Nafion®117) in the presence oh H2O-MeOH mixed solvent for different compositions and temperaturs. We have showed that variations of static characteristics are much more pronounced for Nafion than for CM2, which is explained by the influence of MeOH on the dielectric constant of the membrane phase, by the cross-linking difference, and by the auto-accelarated character of the MeOH penetration in Nafion. The interpretation of the results given by three dynamic characteristics (electrical conductivity (km), MeOH permeability (PM), transport number (TA)) by using the micro-heterogeneous model (to determine the fraction of the intergel phase f2) allowsus to correlate these variations with the MeOH content (XM) and to explain the activation energy (EA) variations. The correlation between km and f2 confirmed KREUER's conclusions relative to MEC microstructures (acquired by SAXS) and showed the limits of the micro-heterogeneous model. The analysis of the curve f2=f XM) allowed us to improve HAUBOLD's model by intriducing a new parameter. The PM measurements showed that Nafion117 presents higher MeOH leakage than CM2, which is attributed to their cross-linking difference. TA measurements showed showed a strong selectivity loss for XM>30%. This is due to a strong electrolyte penetration inside the MEI and the formation of ion-pairs. The modifications of MEI showed that each treatment reduces PM and km, but none permits to have weak PM and high km
Safariamin, Maryam. "Valorisation catalytique du biogaz (CH4 +CO2) par reformage à sec : étude des propriétés physico-chimiques et catalytiques de solides à base de Tuthénium et Cuivre". Littoral, 2010. http://www.theses.fr/2010DUNK0281.
Testo completoIn this study, the reaction of methan reforming with CO2 was investigated in the presence of catalysts based on ruthenium and copper deposited on Al2O3, CeO2-Al2O3 binary oxides and mixed oxides from hydrotalcite precursors. The aim of this work is reduction of greenhouse gases (CH4 + CO2) to obtain the synthesis gas (H2 + CO) to be used for various applications including clean energy. The catalysts were prepared by dry impregnation and characterized by various physico-chemical methods (BET, XRD, FT-IR, UV-VIS, TPR, DTA/TG and EPR) to identify correlations between their physico-chemical properties and their catalytic performance. Influence of different conditions and solids pretreatment on the catalytic activity have been studied. Hydrogen production is strongly influenced by the nature of the metal phase and the support used. It is noteworthy that both types of catalysts (Ru and Cu/support) were not similar activities for the reaction studied. The ruthenium-based catalysts are much more active than those based on copper. Hydrotalcites have proved effective for the reforming reaction, but they produce a large amount of coke which deactivates the catalyst easily. Among all catalysts are studied, the solid containing 5% RuO2 on the support of CeO2-Al2O3 binary oxides was the most active and most stable. The high reactivity of this catalyst is associated to good dispersion of ruthenium species and to the very low amount of coke on the catalyst observed after 14 days of aging
Mirdamadi, Esfahani Malaknaz. "Effets de l'environnement sur les propriétés physico-chimiques des atomes d'argent et des nanoparticules mono-et bimétalliques à base d'or : étude par radiolyse pulsée et stationnaire". Paris 11, 2009. http://www.theses.fr/2009PA112010.
Testo completoThe aim of the present work was to study the physico-chemical properties of silver atoms, monometallic and gold-based bimetallic nanoparticles synthesized by the radiation chemical reduction method. In the first part of thesis, we studied the effects of bromide ligands on the kinetics and spectral properties of the silver atom complex. The rate constant for the reduction of AgIBr43- in aqueous solution was determined by pulse radiolysis and the redox potential of the couples AgIBr43-/Ag0Br44- and AgIBr43-/ Ag0 + Br44- were estimated with the help of thermodynamic cycles. Comparison of the obtained values indicates that the redox potential of the silver atom couple is lowered by bromide ligands and the formation of Ag0Br44- is more favourable than a free silver atom. In the second part, the effects of stabilizing agents on optical, structural and electrocatalytic properties of monometallic nanoparticles, such as gold and iron and bimetallic nanoparticles systems, Au/Fe and Au/Pt, prepared by gamma-radiolysis were studied. Our results offer a new strategy to present the effectiveness of the stabilizing agents in the process of metal ion reduction, in the nanoparticles morphology (shape and size) as well as in the elementary composition of bimetallic nanoparticles. This study indicates that the radiolysis method, which we used for the nanoparticles synthesis, allow us to obtain gold based bimetallic nanoparticles that showed an excellent electrocatalytic activity toward reduction of oxygen and proton as well as oxidation of methanol. Our results show that these systems are very promising for application in fuel cells
Pons, Aenor. "Elaboration, caractérisations et modélisation des mécanismes de conduction de matériaux céramiques conducteurs anioniques et protoniques". Thesis, Limoges, 2014. http://www.theses.fr/2014LIMO0035/document.
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