Добірка наукової літератури з теми "Post-Traitement catalytique"
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Дисертації з теми "Post-Traitement catalytique":
Reneme, Yvan. "Post-traitement catalytique des gaz de combustion de moteurs thermiques fonctionnant au gaz naturel." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10149/document.
This investigation deals with the development of noble metal based catalysts for after-treatment systems dedicated to natural gas engines. The high stability of methane implies more elevated running temperatures than in the conventional three-way technology. Deactivation proceeds more rapidly related to thermal sintering and changes in surface composition when Pd and Rh are associated. The impact of such reconstruction has been evaluated on the adsorptive properties of noble metals and the mechanism involved in the activation of methane. The beneficial effect due to Rh incorporation to Pd/Al2O3 preventing agglomeration of Pd was observed as well as a greater stabilization of the adsorptive properties after oxidative thermal treatment. Pd deposition on Al2O3/CexZr1-xO2 was found to improve the thermal stability and activity associated with an enhancement of OSC properties.The catalyst behaviour has also been studied during the cold start engine where the NO/H2 reaction predominates. Theoretical and experimental approaches were compared in order to propose a mechanism where the elementary key is dissociation of NO. Competitive H2/O2 reaction plays an important role regulating the hydrogen surface coverage which assists the dissociation on Rh. This beneficial effect disappears on Pd/Al2O3 due to a H2/O2 reaction much faster than the NO/H2. Finally, alternative catalyst formulations were developed based on perovskite. The potential interest of such materials is related to their ability to stabilize the metal dispersion of noble metals and to improve the oxygen storage capacity particularly when Pd is included in the perovskite lattice rather than deposited by impregnation
Anguita, Paola. "Impact des biocarburants sur le système d’oxydation catalytique des véhicules diesel." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1181.
The more restrictive regulations to reduce pollutants emissions, especially CO2, promote the use of biofuels. However, biodiesel contains inorganic elements (Na, K, Ca and P) that reduce the durability of the after-treatment catalysts. This work aims to evaluate the performance of Diesel Oxidation Catalysts (DOCs, PtPd/CeZrO2/La-Al2O3 reference catalyst). The characterization results have shown that the above-mentioned impurities affect the physico-chemical, redox, surface and catalytic properties. Although the catalyst crystalline structure of reference catalyst did not change after impurities incorporation, the specific surface area decreased. The redox ability was also decreased when Na, K and Ca impurities are present due to their low electronegativity, which increased the oxygen interaction. This high interaction seems to be responsible of the enhanced C3H6 reaction rate. NO-TPD results evidenced that the high basicity of Na, K and Ca impurities resulted in an increase of NO adsorption strength. Accordingly, DRIFT results showed the presence of NO intermediates adsorption associated to the electrostatic field created by these cations, hindering NO oxidation. CO adsorption was also promoted, enhancing CO reaction rate. The formation of cerium phosphate was also observed, which could stabilize the Ce3+ oxidation state (checked by XPS), decreasing NO oxidation due to the blockage of catalytic sites. Nevertheless, CO and C3H6 co-oxidations were enhanced by avoiding self-poisoning. After catalyst hydrothermal aging, the effect of impurities was masked by the sintering of Pt/Pd active sites, which decreases the DOC catalytic performances
Bonfils, Anthony. "Commande expérimentale en boucle fermée des systèmes de post-traitement SCR en utilisant des sondes à NOx sensibles au NH3." Thesis, Paris, ENMP, 2013. http://www.theses.fr/2013ENMP0097/document.
The problem studied in this thesis is the closed-loop control of a urea-SCR (urea Selective Catalytic Reduction) as used in aftertreatment systems of diesel vehicles. A first contribution of the thesis is a detailed model for the SCR, highlighting the distributed (1D) nature of the considered system, and several successive reductions of this simulation model leading to a simpler one, better-suited for control design purposes. A second contribution consists in considering the sensitivity to NH3 of the NOx sensor used in a feedback loop, in the development of the control algorithms (state observer, feedback, gain scheduling, measurement interpretation). The ambiguity of the output measurement could be detrimental to the closed loop response, as it generates multiple equilibrium points (artefacts), besides the point of practical interest. A study of the closed-loop dynamics is performed in the vicinity of each point, which shows that the closed loop system naturally converges to the point of interest not to the artefacts. Both contributions have been tested and validated experimentally. In summary, the method proposed in this thesis might allow an engine equipped with Euro 5 hardware to satisfy Euro 6 standard using a preconditioning procedure of the catalyst
Zheng, Yuanshuang. "Intelligent end-of-pipe catalytic systems suited for alternative fuels." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR038.
The objective of this thesis work is to develop catalysts based on perovskite and palladium for the treatment of traces of methane from vehicles running on natural gas. In more detail, the study is based on the combination of two active catalysts, each having a role in the targeted reaction - the catalytic combustion of methane. Perovskites based on LaMnO3 composition with excellent high temperature methane oxidation activity are used as carriers. Among them, the non-stoichiometric study of lanthanum and the partial substitutions of lanthanum by potassium and strontium have been used to modify the structure of perovskite to generate distortions for better catalytic activity and mobility of the oxygen. Palladium, recognized as a noble metal with excellent low temperature methane catalytic performance, has been incorporated into perovskite catalysts by different calcination methods (i.e. one-pot method and sequential method by synthesis of the sol-gel method of citric acid). Given the consideration of cost control, the objective is to reduce the use of palladium as much as possible, from 1% to 0.5% by mass in the experiment. Therefore, low palladium boosted perovskite composite catalytic system is the research strategy of this topic around catalytic methane combustion. In order to study the physicochemical properties of catalysts, characterization methods such as thermogravimetric analysis, X-ray diffractometry, N2-physisorption, H2-temperature-programmed reduction, O2-temperature-programmed oxidation, O2-temperature-programmed desorption/mass spectrometry, scanning electron microscopy/energy dispersive X-ray spectroscopy, transmission electron microscopy/energy dispersive X-ray spectroscopy, X-ray photoelectron spectrometry and Inductively Coupled Plasma Mass Spectrometry are used to analyze surface and bulk properties of target catalysts.The second part of this thesis was devoted to the kinetics of methane oxidation by the high-throughput reaction method. The study of the kinetics was carried out by the approach through the theoretical and experimental combination to study the mechanisms of the different proposals of the active sites and the source of reactive species of active oxygen before and after aging. Moreover, in the whole reaction process, the catalysts with different palladium incorporation methods exhibit the different reaction mechanisms. This study is instructive to investigate the nature and synergy of methane oxidation on palladium-boosted perovskite and the factors influencing catalyst design.In practice, this combination of catalysts has been used as three-way catalysts for simulated gas aftertreatment of natural gas engines. The catalysts were tested in the laboratory-scale plug-flow reactor according to the same experimental plan as the kinetic part. In the current of methane traces, the reaction becomes more difficult and more complicated in the presence of NO, CO, water vapor and CO2. The complete oxidation of methane, the partial oxidation of methane, the reduction of NO to nitrogen or even to ammonia have been discovered and investigated by the reaction budget.Keywords: Perovskite / Methane Oxidation / Palladium / Catalytic Aftertreatment / Natural Gas Engine
Wu, Jianxiong. "Développement de nouveaux matériaux catalytiques à faible teneur en métaux précieux pour le post-traitement des gaz d'échappement automobiles." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R021/document.
The current study aims to develop novel catalytic materials for the post-treatment of exhaust gas stemming from gasoline engines. The Three Way Catalyst (TWC) is generally considered as a mature and reliable technology capable of removing simultaneously the main pollutants present in the automobile exhaust gas: CO, HC and NOx. The existing TWC system relies heavily on the significant use of Platinum Group Metals (PGMs) and Rare Earth Elements (REEs). However, the high-cost and scarcity of the conventional PGM-based TWC system constitutes an obstacle for the cost reduction of exhaust gas treatment technology as well as a severe burden on natural resource. Another drawback of conventional TWC is associated with the sintering of precious metals in the process of catalyst operation and unsatisfactory N2 selectivity during NOx reduction. Therefore, alternative solutions are required which should ideally allow a substantial reduction of PGMs usage without sacrificing significantly the catalytic performance. Trois voiesThe goal of this study is to evaluate the feasibility of applying perovskite-type materials as an alternative to the replacement of conventional TWC system. The main approach employed is composition optimization of perovskite-type materials, including creation of non-stoichiometry in the chemical composition, partial substitution in A or B site and addition of small amount of PGMs. Influence of partial substitution in A or B site as well as the synergistic effect of dual substitutions in both A and B site were investigated. Results showed that Cu doping in B site could enhance oxidation of CO and C3H6 while Mn doping had a noticeable promoting impact on NO reduction under stoichiometric conditions. Small amount of PGM loading combined with doping of Cu or Mn could enhance remarkably the redox properties of the lanthanum ferrite perovskite. Ca doping in A site affected the dispersion and diffusion of precious metals across the perovskite substrate. The PGM-loaded perovskite catalysts outperformed the commercial benchmark catalyst in terms of higher NO conversion and N2 selectivity in stoichiometric condition in the operating temperature range of the TWC system but the deNOx activity during cold-start process remains a big challenge
Wu, Jianxiong. "Développement de nouveaux matériaux catalytiques à faible teneur en métaux précieux pour le post-traitement des gaz d'échappement automobiles." Electronic Thesis or Diss., Université de Lille (2018-2021), 2019. http://www.theses.fr/2019LILUR021.
The current study aims to develop novel catalytic materials for the post-treatment of exhaust gas stemming from gasoline engines. The Three Way Catalyst (TWC) is generally considered as a mature and reliable technology capable of removing simultaneously the main pollutants present in the automobile exhaust gas: CO, HC and NOx. The existing TWC system relies heavily on the significant use of Platinum Group Metals (PGMs) and Rare Earth Elements (REEs). However, the high-cost and scarcity of the conventional PGM-based TWC system constitutes an obstacle for the cost reduction of exhaust gas treatment technology as well as a severe burden on natural resource. Another drawback of conventional TWC is associated with the sintering of precious metals in the process of catalyst operation and unsatisfactory N2 selectivity during NOx reduction. Therefore, alternative solutions are required which should ideally allow a substantial reduction of PGMs usage without sacrificing significantly the catalytic performance. Trois voiesThe goal of this study is to evaluate the feasibility of applying perovskite-type materials as an alternative to the replacement of conventional TWC system. The main approach employed is composition optimization of perovskite-type materials, including creation of non-stoichiometry in the chemical composition, partial substitution in A or B site and addition of small amount of PGMs. Influence of partial substitution in A or B site as well as the synergistic effect of dual substitutions in both A and B site were investigated. Results showed that Cu doping in B site could enhance oxidation of CO and C3H6 while Mn doping had a noticeable promoting impact on NO reduction under stoichiometric conditions. Small amount of PGM loading combined with doping of Cu or Mn could enhance remarkably the redox properties of the lanthanum ferrite perovskite. Ca doping in A site affected the dispersion and diffusion of precious metals across the perovskite substrate. The PGM-loaded perovskite catalysts outperformed the commercial benchmark catalyst in terms of higher NO conversion and N2 selectivity in stoichiometric condition in the operating temperature range of the TWC system but the deNOx activity during cold-start process remains a big challenge
Monna, Virginie. "Réactivité des décharges en flux dans les mélanges de gaz pour le traitement des surfaces." Toulouse 3, 2002. http://www.theses.fr/2002TOU30051.
The necessity to develop "clean" processes in the world of material treatments, pushes the industry to look about plasmas processes. This thesis tells about the use of a flowinf post-discharge reactor, at low pressure, for different surface treatments: metallic (aluminium and titanium) surface preparation for adhesion and sterilisation of medical instruments. First, the creation mechanisms in the microwave plasmas formed by gas mixtures (Ar, H2, O2, N2 and H2O) and the destruction of the atomic species H and O in the post-discharge are analysed by spectroscopic means and catalytic probes. Secondary, the treatments are tested in a modulated post-discharge reactor in CPAT. The influence of the experimental parameters is observed by the substrate analysis (FTIR, ESCA, tree points flexion mechanical tests and bacteria culture). .