La pollution atmosphérique malodorante provient essentiellement de quatre gaz SO2, H2S, NO2 et NH3. Afin de réduire au mieux ces effets néfastes sur la santé et l'environnement, il faut contrôler en continu les émanations de gaz le plus près possible de la source. Ce qui nécessite un appareil capable de détecter ces gaz polluants, simple d'utilisation, de taille et poids réduits. C'est dans cette optique que nous avons réalisé un nez électronique portable, servant à détecter les quatre gaz cibles déjà cités. La partie sensible de ce prototype est constituée d'une matrice de six capteurs à oxydes métalliques semi-conducteurs, dont nous utilisons la sensibilité croisée. Le nez électronique fonctionne sur le même principe que le nez humain, il doit apprendre à reconnaître une odeur. Cette phase d'apprentissage se déroule au laboratoire où nous envoyons sur les capteurs des mélanges gazeux connus et contrôlés. La réponse des capteurs varie en fonction de la nature du gaz (réducteur ou oxydant) et de leur sensibilité à celui-ci. Puis l'utilisation de méthodes d'analyse de données a prouvé que notre nez électronique peut discriminer un mélange gazeux complexe et le quantifier. Ensuite nous avons placé le nez électronique en situation réelle, en étudiant l'odeur dégagée par des fientes de canards dans une ferme expérimentale. Les résultats obtenus ont montré que cet appareil pouvait détecter de manière fiable les variations d'odeur en fonction des paramètres influents. Ainsi, nous avons réalisé la validation de notre prototype en laboratoire puis sur site. Mais les capteurs utilisés présentent un inconvénient, ils doivent conserver sans interruption leur température de fonctionnement (~ 350°C). Afin de prévenir cette forte consommation d'énergie, nous avons développé des capteurs polymères qui fonctionnent à température ambiante. La caractérisation en laboratoire a montré qu'ils sont sensibles aux gaz cibles étudiés. Leurs réponses à H2S laisse apparaître une bonne stabilité à court et moyen terme, qui permettra de les intégrer dans la matrice après complet développement / The malodorous atmospheric pollution results essentially from four gases SO2, H2S, No2 and NH3. To reduce at best these fatal effects on the health and the environment, it is necessary to control continuously the gas emanations closer to the source, That requires adevice enable to detect these polluant gases, easy to use, with reduced size and weight. In this way, we have realized a portable electronic nose, to detect of the four target gases already mentioned. The sensitive part of this prototype is composed of a matrix of six semi conducting metal oxide sensors, offering a good cross sensivity. The electronic nose mimics the human nose, he has to learn to recognize an odour. This learning phase is realised in the laboratoy by introducing in the sensor cell gas mixtures with controlled composition, The sensor response varies with the nature of the gas (reducing or oxidizing) and their own gas sensitivity. The use of analysis and data methods proves that our electronic nose can well discriminate a complex gas mixture and quantify it. Then, we have placed the electronic nose in a real situation, by studying the odour coming from a duck experimental farm. The obtained results showed that this prototype could well detect the variations of the odour level in accordance with the influent parameters. So, we have realized the laboratory and the real site validation of our electronic nose. But the metal oxide sensors present an inconvenient : they have to keep continuously their working temperature (~ 350°C). To prevent this strong energy consumption, we have developed polymer sensors which work at room temperature. The characterization in laboratory showed that they are sensitive to studied target gases. Their responses to H2S have a good stability in short and middle term, allowing to integrate them into the matrix after complete development

This work provides a detailed characterization study on H2S poisoning of Pd and Pd/Au alloy composite membranes to obtain fundamental understandings of sulfur poisoning phenomena and preparation of sulfur tolerant membranes. The enhancement of the sulfur tolerance by alloying Pd with Au has been confirmed by both permeation test and microstructure analysis (SEM and XRD). While pure Pd membranes exhibited the permeance decline in the presence of H2S due to both sulfur adsorption and bulk Pd4S formation, Pd/Au alloy membranes showed the permeance loss merely resulted from the surface sulfur adsorption without bulk sulfide formation up to 55 ppm H2S. The XPS study confirmed that the H2S adsorption on the Pd/Au alloy surfaces was dissociative, and both surface Au and Pd sulfides were formed with the preferential Au-S bonding. The adsorption type of sulfur on the Pd/Au alloy surfaces was monolayer with a limited coverage, which increased with decreasing temperature. The permeance loss of Pd/Au membranes was essentially fully recoverable in H2, and the integrity of the membranes remained unaltered after the poisoning/recovery tests. Increasing Au composition in the Pd/Au membranes increased the sulfur tolerance. A Pd/Au alloy membrane of 16.7 wt% Au exhibited a permeance over 50% of its original value in the presence of 5 ppm H2S at 400°C, while a Pd membrane showed 85% permeance loss. The Pd/Au alloy membranes were fabricated by the Au displacement deposition, which had an empirical reaction order of 3.2 determined by the AAS. The HT-XRD study verified that the formed Pd/Au alloy layers were thermally stable up to 500°C.

The ability to detect and quantify presence and concentration of unknown gasses is sought for applications ranging from environmental monitoring to medical analysis. Metal oxide based chemical sensing technology currently exists but the ability to provide a compositional gas breakdown reliably within a short time frame is not readily available. A very small sensor that can differentially identify the type and concentration of a gas is required. Novel methods of creating low cost and easily tuned one and two-dimensional gas sensing elements are explored. Tungsten trioxide has been thoroughly documented as an electrochromic coating, but highly sensitive WO3 elements with beam and nanowire structures have yet to be explored. Research of WO3 as a gas sensor encompasses three major components: A suitable sensing chamber with accurate analyte gas flow control and temperature control, a reliable method for WO3 deposition, and a high yield fabrication process. This thesis explores all three of these technologies. Chapter two starts with a summary of existing tungsten trioxide fabrication methods. An overview of WO3 processing follows. A comprehensive setup was designed and created to test the gas sensing response of a series of metal oxide based resistive elements through conductimetric analysis. Chapter three provides an in depth account of gas sensor test chamber design and testing. Critical test chamber aspects such as temperature control, precise gas flow control, highly efficient analyte gas switching and ease of use are presented. Chapter four outlines WO3 electrodeposition and the fabrication of beam structures for testing, while chapter five explores the templated electrodeposition of WO3 segments intercalated between gold nanowire segments. Finally, chapter six provides a summary of the research presented in this thesis as well as future directions and options available for further exploration of WO3 gas sensing elements. / Micro-Electro-Mechanical Systems (MEMS) and Nanosystems

Die vorliegende Arbeit befasst sich mit Untersuchungen zur Trockenentschwefelung von Brenngasen durch Partialoxidation von H2S an Herdofenkoks. Hierzu wurden Versuche in der Technikumsanlage VTE 2004 mit einem simulierten PHTW Gas durchgeführt. Es zeigte sich, dass der COS-Abbau nicht wie bisher angenommen durch die COS-Partialoxidation sondern durch die COS-Hydrolyse erfolgt. Die COS-Hydrolyse gewinnt dabei mit abnehmender Raumbelastung an Bedeutung. Der Entschwefelungsgrad erhöht sich mit steigendem Sauerstofffaktor und abnehmender Raumbelastung. Sauerstofffaktoren >4 sind aufgrund des vollständigen H2S-Umsatzes und der nicht ablaufenden COS-Partialoxidation nicht sinnvoll. Die Gewinnung des abgeschiedenen Schwefels auf dem Herdofenkoks konnte nachgewiesen werden. Abschließende Berechnungen ergaben, dass sich mit den erreichten Schwefelkonzentrationen im Reingas das Verfahren im aktuellen Entwicklungsstand für die Vorentschwefelung im IGCC-Kraftwerk eignet.

Shallow marine gas hydrates occurring above the Sulfate-Methane-Interface (SMI) often contain small amounts of H2S beside methane and other hydrocarbons, but the distribution of H2S in these natural samples is not always homogeneous. To learn more about the formation of H2Scontaining hydrates, gas hydrates with different ratios of H2S/CH4 were synthesized under various conditions. The samples were synthesized from ice and water phases, with constant feed gas compositions or controlled changes in feed gas compositions. It turns out that the detailed nature of the synthetic hydrate samples depends on the method of sample preparation. The sample prepared with gas containing small amounts of H2S (1% H2S and 99% CH4) appeared homogeneous in composition, while that prepared in a water-H2S-CH4 system with higher H2S contents was heterogeneous. The samples were analysed with Raman spectroscopy, and differential scanning calorimetry (DSC).

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No description available.

Il est couramment admis que le niveau de pollution dans l'environnement intérieur pouvait dépasser le niveau de pollution extérieur. C'est la raison pour laquelle la qualité de l'air intérieur est devenue une préoccupation sociétale importante en raison de la durée croissante que nous passons dans ces environnements. Les procédés d'oxydation avancée (POA), parmi lesquels l'oxydation photocatalytique, sont des techniques pertinentes pour la purification de l'air. En photocatalyse, les nanotubes de titane montrent un intérêt tout particulier en raison de leurs propriétés intrinsèques spécifiques de par leurstructure tubulaire. Ce matériau unidimensionnel engendre un rapport surface/volume important qui donne accès à une surface spécifique et à des capacités d'adsorption importantes, mais aussi à des propriétés de transport électronique accrues. Deux molécules modèles gazeuses ont été retenues, la méthyléthylcétone (MEC) et le sulfure de dihydrogène (H2S). Ces molécules diffèrent de par leur composition chimique (présence ou non d'hétéroatomes) et leurs propriétés physico-chimiques et reflètent différentes catégories de pollutions chimiques et olfactives. Afin d'améliorer les performances photocatalytiques des nanotubes, de TiO2 synthétisés par méthode hydrothermale, que ce soit sous illumination UV-A ou solaire, des modifications avec un autre semi-conducteur WO3 ou ZnO ont été entreprises. Les mêmes modifications ont également été réalisées sur le photocatalyseur commercial TiO2 P25 (Evonik). Une des finalités de ce travail est la corrélation des conditions de synthèse de ces matériaux avec leurs caractéristiques physico-chimiques et avec leurs propriétés photocatalytiques vis-àvis de l'élimination des deux polluants étudiés. Une approche mécanistique a également été menée.

Electricity and power generation is an essential part of our life. However, powergeneration activities also create by-products (such as sulphur oxides, nitrogen oxides,carbon monoxide, etc), which can be dangerous when released to the atmosphere.Sensors, as part of the control system, play very vital role for the fluegas cleaning processes in power plants. This thesis concerns the development ofSilicon Carbide Field Effect Transistor (SiC-FET) gas sensors as sensors for sulfurcontaining gases (SO2 and H2S) used as part of the environmental control systemin power plants. The works includes sensor deposition and assembly, sensinglayer characterization, operation mode development, performance testing of thesensors in a gas mixing rig in the laboratory and field test in a desulfurization pilotunit, and both experimental and theoretical studies on the detection mechanismof the sensors. The sensor response to SO2 was very small and saturated quickly. SO2 is a verystable gas and therefore reaction with other species requires a large energy input.SO2 mostly reacts with the catalyst through physisorption, which results in lowresponse level. Another problem was that once it finally reacted with oxygen andadsorbed on the surface of the catalyst in form of a sulfate compound, it is desorbedwith difficulty. Therefore, the sensor signal saturated after a certain timeof exposure to SO2. Different gate materials were tested in static operation (Pt,Ir, Au), but the saturation phenomena occurred in all three cases. Dynamic sensoroperation using temperature cycling and multivariate data analysis could mitigatethis problem. Pt-gate sensors were operated at several different temperatures in acyclic fashion. One of the applied temperatures was chosen to be very high for ashort time to serve as cleaning step. This method was also termed the virtual multisensor method because the data generated could represent the data from multiplesensors in static operation at different temperatures. Then, several features of thesignal, such as mean value and slope, were extracted and processed with multivariatedata analysis. Linear Discrimination Analysis (LDA) was chosen since itiiiallows controlled data analysis. It was shown that it was possible to quantify SO2with a 2-step LDA. The background was identified in the first step and SO2 wasquantified in the second step. Pt sensors in dynamic operation and 2-step LDAevaluation has also demonstrated promising results for SO2 measurement in thelaboratory as well as in a desulfurization pilot unit. For a commercial sensor, algorithmhave to be developed to enable on-line measurement in real time. It was observed that Ir-gate sensors at 350oC were very sensitive to H2S. The responseobtained by Ir sensors to H2S was almost five times larger than that of Ptsensors, which might be due to the higher oxygen coverage of Ir. Moreover, Irsensors were also more stable with less drift during the operation as a result ofhigher thermal stability. However, the recovery time for Ir sensors was very long,due to the high desorption energy. Overall, the Ir sensors performed well whentested for a leak detection application (presence of oxygen and dry environment).The geothermal application, where heat is extracted from the earth, requires thesensor to be operated in humid condition in the absence (or very low concentration)of oxygen, and this poses a problem. Temperature cycle operation and smartdata evaluation might also be an option for future development. Along with the sensor performance testing, a study on the detection mechanismwas also performed for SO2 sensor, both experimentally and theoretically. The experimentincluded the study of the species formed on the surface of the catalystwith DRIFT (diffuse reflectance infrared frourier transform) spectroscopy and theanalysis of the residual gas with mass spectroscopy. Explanatory investigation ofthe surface reactions was performed using quantum-chemical calculations. Theoreticalcalculations of the infrared (IR) vibration spectra was employed to supportthe identification of peaks in the DRIFT measurement. Based on the study on theresidual gas analysis and quantum-chemical calculations, a reaction mechanismfor the SO2 molecule adsorption on the sensor surface was suggested.

The slags from iron-steel and zinc industries are rich in metal oxide contents like FeO, MnO, CaO. However, these slags are not used extensively, except some usage in the cement industry. These slags can be used in removing H2S from waste gases from different industrial sources. The purpose of this research is to study the effect of initial concentration of H2S on the capacity and sorbent efficiency of waste materials from iron-steel and zinc industries. Experiments were conducted in a 25 mm-quartz reactor with simulated gases containing H2S as reactive gas. Breakthrough curves for sulfidation reactions were obtained for 3000 ppmv, 4000 ppmv and 5000 ppmv initial H2S concentrations at the reaction temperature range of 500&deg / C&ndash / 700&deg / C. According to the results obtained from the experiments, the H2S removal capacity of both slags increased with increasing reaction temperature, however, the H2S removal capacity of the slags decreases as the initial H2S concentration increases. Cyclic sulfidation and regeneration tests were applied to both steel and zinc slags in order to determine the regenerability of the slags. In cyclic tests, zinc slag gave better results than steel slag. A &ldquo / Deactivation Model&rdquo / was used in order to fit the breakthrough curves obtained experimentally to the breakthrough curves predicted from the deactivation model. A very good fit was obtained for both steel and zinc slags. Zinc slag was shown to be more suitable for gas cleanup than steel slag taking into account its high H2S removal efficiency, regenerability and low cost (almost free of charge).