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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Vers une maitrise de l'impact réel des choix de conception sur la qualité de l'air intérieur des bâtiments tout au long de leur vie. / Towards mastering the real impact of design choices on the indoor air quality of buildings throughout their lives.

Gross, Alexandre 10 December 2018 (has links)
Un des enjeux pour améliorer la qualité de l’air intérieur des bâtiments est d’adopter de bonnes pratiques, notamment en matière de sélection des matériaux lors des phases de conception. Pour cela, des outils d’aide à la décision/conception sont indispensables en support à ces bonnes pratiques pour atteindre une maîtrise globale de la qualité de l’air intérieur. Dans le domaine du bâtiment, il n’existe pas à ce jour d’outil opérationnel permettant d’estimer, en amont d’une construction, la qualité de l’air intérieur. Des travaux sont engagés sur ce thème mais ils se heurtent à un manque d’informations sur le comportement des matériaux lorsque ceux-ci sont associés et soumis à des conditions normales d’usage. Ces travaux de thèse avaient donc pour objectif d’évaluer le comportement de matériaux (source ou puits) vis-à-vis de la contamination aux composés organiques volatils (COV) et au formaldéhyde lorsqu’ils sont évalués seuls dans des conditions normalisées retenues pour l’étiquetage sanitaire, mais aussi lorsqu’ils sont mis en œuvre dans des projets de construction (impact du changement d’échelle et effet d'assemblage). La méthodologie développée a donc associé des essais à l’échelle du matériau et à l’échelle d’une pièce dans le but d’acquérir des données d’entrée à un modèle pour la prédiction des concentrations et l’évaluation des contributions respectives des différents processus (émissions primaires, échanges aux interfaces air/surfaces intérieures,…) à la contamination intérieure par les COV. Une première partie de ce travail a consisté à évaluer en laboratoire les échanges de COV et de formaldéhyde à l'interface matériau-air pour une sélection de matériaux de construction et de décoration. Les émissions primaires ont été déterminées selon la méthode normalisée ISO 16000-9 et par une méthode d’échantillonnage passif basée sur un couplage cellule d'émission/micro-extraction sur phase solide (SPME) (dispositif DOSEC-SPME) et l’effet de l’assemblage de matériaux et de composants sur la qualité de l’air intérieur a été étudié. Les constantes d’adsorption/désorption du formaldéhyde sur les matériaux sélectionnés ont ensuite été déterminées par une méthodologie innovante. Ces constantes, ainsi que les données d’émission, ont été rassemblées dans une base données pour servir de critères (ou indicateurs) pour la sélection de matériaux respectueux de la qualité de l’air intérieur (QAI). Dans une deuxième partie, les résultats obtenus en conditions de laboratoire ont été confrontés à ceux obtenus en conditions réelles à l’échelle d’une pièce dans le cadre d’une étude de plusieurs mois dans le but de mettre en évidence l’impact du changement d’échelle. La dernière partie de cette thèse a consisté à développer un modèle de prévision de la QAI intégrant les données d'adsorption/désorption préalablement déterminées. A terme, la base de données et le modèle ont vocation à constituer des outils de gestion pour orienter les choix en matière de matériaux, de configuration et d'usage d’un bâtiment dans l’optique d’une réduction à la source des émissions de COV dans l’air intérieur. / One of the challenges for improving the indoor air quality of buildings is to adopt good practices, especially in the selection of materials during design phases. To this end, decision-making / design tools are essential in support of these good practices to achieve global control of indoor air quality.In the building sector, there is currently no operational tool to estimate the indoor air quality in building. Work is underway on this theme, but they encounter a lack of information on the behavior of materials when they are associated and subject to normal conditions of use.The purpose of this thesis was therefore to evaluate the behavior of materials (source or sink) with respect to contamination with volatile organic compounds (VOCs) and formaldehyde when they are evaluated alone under standardized conditions selected for health labeling, but also when they are implemented in construction projects (impact of the change of scale and the effect of assembly). The developed methodology has therefore combined material-scale and room-scale testing to acquire input data to a model for concentration prediction and assessment of the respective contributions of different processes (primary emissions, exchanges at air / interior surfaces interfaces, ...) to internal contamination by VOCs.A first part of this work consisted of laboratory evaluation of VOC and formaldehyde exchanges at the material-air interface for a selection of construction and decoration materials. The primary emissions were determined according to the ISO 16000-9 standard method and a passive sampling method based on solid-phase emission / micro-extraction (SPME) (DOSEC-SPME device) and the effect of the assembly of materials and components on indoor air quality has been studied. The adsorption / desorption constants of formaldehyde on the selected materials were then determined by an innovative methodology. These constants, as well as emission data, have been collated into a database to serve as criteria (or indicators) for the selection of IAQ-compliant materials.In a second part, the results obtained under laboratory conditions were compared with those obtained under real-world conditions on a scale of a part in a study of several months in order to highlight the impact of the change of scale.The last part of this thesis consisted in developing an IAQ prediction model integrating previously determined adsorption / desorption data. Ultimately, the database and the model are intended to constitute management tools to guide the choice of materials, configuration and use of a building with a view to reducing emissions at the source VOC in the indoor air.
162

Oxydation totale des Composés Organiques Volatils (COV) sur des catalyseurs à base de métaux de transition préparés par voie hydrotalcite : Effet des micro-ondes sur la méthode de synthèse / Total oxidation of Volatil Organic Compounds (VOC) on transition metal catalysts prepared via the hydrotalcite route : effect of the microwave irradiations on the synthesis method

Abou Serhal, Cynthia 04 December 2018 (has links)
Ce travail vise l'étude de l'oxydation catalytique des Composés Organiques Volatils (COVs). L'objectif principal est de trouver des matériaux catalytiques qui sont des alternatives aux métaux nobles très onéreux. La recherche des matériaux catalytiques actifs, sélectifs, stables dans le temps et à base de métaux de transition est abordée. Afin d'améliorer les performances catalytiques des métaux de transition, la dispersion de l'espèce métallique doit être optimisée en utilisant une méthode de synthèse adéquate. Les différents solides préparés ont été caractérisés par différentes techniques physico-chimiques : la Diffraction des Rayons X (DRX), les Analyses Thermiques (ATD/ATG), la Spectroscopie Infrarouge (IR), la Réduction en Température Programmée (H₂-RTP), la Microscopie Electronique à Balayage (MEB), la Spectroscopie de Photoélectrons induits par rayons X (SPX)...De plus, les oxydes obtenus ont été testés dans les réactions d'oxydation totale du COV propène. En premier lieu, nous avons focalisé notre travail sur la préparation d'une série d'oxydes mixtes Co-Mg/Al-Fe par voie hydrotalcite afin d'obtenir des propriétés intéressantes en catalyse hétérogène. Cette étude consiste surtout à évaluer la substitution des cations bivalents et trivalents. Il s'est avéré que le solide contenant à la fois du cobalt et du fer (CoFe) possède l'activité catalytique la plus élevée. L'intérêt de la voie hydrotalcite par rapport à d'autres méthodes de synthèse, telles que la méthode classique et le mélange mécanique des oxydes a été mis en évidence. En second lieu, l'utilisation des irradiations micro-ondes lors de la synthèse des matériaux hydrotalcites a été également étudiée comme une méthode de synthèse non-conventionnelle. Un effet bénéfique a été observé avec l'utilisation des micro-ondes dû principalement à des surfaces spécifiques plus élevées et à une meilleure réductibilité des espèces oxydes. En outre, cette étude vise également la mise au point de cette nouvelle méthode. De ce fait, l'optimisation de la température, durée et puissance des irradiations micro-ondes a été effectuée sur le solide CoFe, afin de montrer l'influence de chaque paramètre sur les propriétés physico-chimiques des matériaux. En troisième lieu, la synthèse d'une série de catalyseurs par voie hydrotalcite avec différentes teneurs en Co²⁺ et Fe³⁺ a été effectuée. L'influence du rapport molaire sur la structure hydrotalcite a été montrée. Une comparaison entre ces solides et ceux préparés par la méthode micro-ondes a été également abordée. / This work aims to study the catalytic oxidation of Volatile Organic Compounds (VOCs). The main objective is to find catalytic materials that are alternatives to very expensive noble metals. The search for transition metal based catalysts is investigated. Furthermore, to improve the catalytic performance of the transition metals, their dispersion must be optimized using an adequate synthetic method. The various prepared solids were characterized by different physicochemical techniques : X-ray Diffraction (XRD), Thermal Analysis (TDA/TGA), Infrared Spectroscopy (IR), Temperature Programmed Reduction by hydrogen (H₂-TPR), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS)...Moreover, the obtained oxides were tested in the total oxidation of the VOC propene. Firstly, we focused our work on the preparation of a series of Co/Fe hydrotalcites -like samples by the traditional co-precipitation method. This study consists mainly of evaluating the substitution of bivalent and trivalent cations. It has been found that the solid containing both cobalt and iron (CoFe) has the highest catalytic activity. The interest of the hydrotalcite route compared to other methods of synthesis, such as the classical method and the mechanical mixing of oxides was put into evidence. Secondly, the use of microwave irradiation during the synthesis of hydrotalcite materials has also been studied as an unconventional method of synthesis. A beneficial effect has been observed with the use of microwaves due mainly to higher specific surface areas and better reducibility of the oxide species. In addition, an optimization of the temperature, duration, and power of the microwave irradiations was carried out on the CoFe solid, in order to show the influence of each parameter on the physico-chemical properties of the materials. Thirdly, the synthesis of a series of hydrotalcite catalysts with different ratio of Co²⁺ and Fe³⁺ was carried out. The influence of the molar ratio on the hydrotalcite structure has been shown. A comparison between these solids and those prepared by the microwave method was also discussed.
163

Etude de la dégradation catalytique simultanée de NOx/COV sur des oxydes mixtes à base de cuivre et de fer / Study of the simultaneous catalytic degradation of NOx/VOC over copper and iron mixed metal oxides

Mrad, Raya 11 January 2016 (has links)
Dans le cadre de la politique de réduction des émissions de gaz toxiques tels que les composés organiques volatils (COV) et les oxydes d'azote (NOx), cette étude portait sur la mise au point de catalyseurs exempts de métaux nobles, efficaces pour l'élimination simultanée des COV (propène) et des NOx en présence d'un excès d'oxygène (milieu pauvre). Deux traitements ont été envisagés : d'une part nous avons étudié la réaction d'oxydation totale du propène et d'autre part les réactions simultanées d'oxydation du propène et de réduction des NOx. Le choix s'est reporté sur les matériaux hydrotalcites qui, après calcination, permettent d'obtenir un mélange d'oxydes ayant des propriétés intéressantes en catalyse. Dans un premier temps, des catalyseurs massiques à base de Cu, de Mg et de Al ont été synthétisés par voie hydrotalcite. Nous avons pu mettre en évidence que les espèces cuivriques sous formes de petits agrégats de CuO très dispersés à la surface sont actifs pour la réduction des NOx alors que les ions CU²⁺ sous forme de cristallites de CuO sont plus actifs dans l'oxydation du propène. Afin d'améliorer les performances catalytiques de ces catalyseurs, l'incorporation de l'élément Fe dans ces matériaux a été réalisée. Pour la réaction de réduction des NOx en présence de C₃H₆, la coexistence du fer et du cuivre dans un même matériau décale la fenêtre de température de conversion des NOx vers de plus basses températures mais également diminue la conversion de NO. Par ailleurs, en vue d'accroître les valeurs de conversion de NOx, le catalyseur qui convertit le mieux les NOx a été promu par des métaux alcalins. Cs et Na ont montré un effet promoteur tandis que K a exercé un effet inhibiteur dans la réaction de réduction des NOx. Dans la dernière partie de ce travail, une introduction à l'oxydation catalytique des suies et à l'élimination simultanée du propène et des NOx en présence de suies a été envisagée. Une autre partie du travail de thèse a concerné les particules atmosphériques qui ont été collectées au Liban durant une tempête désertique provenant du désert Arabe, le but étant d'évaluer le changement morphologique et chimique qui peut avoir lieu au cours du transport à longue distance. La caractérisation de ces particules par microcopie électronique à balayage couplée à un Spectromètre à Dispersion d'Energie a montré que les grosses particules sont riches en oxydes métalliques (notamment en Si, Al, Mg, Fe, Ca...). Sur les particules fines et ultrafines nous avons pu mettre en évidence la formation d'oligomères d'organonitrates et d'organosulfates. Or, ces organonitrates proviennent de la réaction entre les COV et les NOx. / This thesis was done within the politics of reducing the emissions of toxic gases such as volatile organic compounds (VOC) and nitrogen oxides (NOx). This study aimed to optimize efficient catalysts, prepared in the absence of noble metals, for the simultaneous elimination of VOC (propylene) and NOx under excess of oxygen (lean condition). Hydrotalcite solids were chosen because of the interesting properties of the oxides obtained by their calcination. Two treatments were performed : on the one hand the propylene oxidation alone, on the other propylene oxidation and NOx reduction simultaneously. Cu, Mg and Al - based catalysts were prepared by the hydrotalcite route. The as-prepared solids were proven to be efficient in the NOx reduction due to the presence of small aggregates of well dispersed CuO on the surface. However the CU²⁺ ions in the forms of crystallites were active in the propylene reaction. In order to improve the catalytic activity, Fe element was then incorporated into the solids to substitute a part or all of the Al element and the effects were studied. In the selective catalytic reduction of NOx by the C₃H₆ the introduction of iron species into the structure lowered the temperature of complete C₃H₆ conversion but also reduced the NOx conversion. Moreover, in order to improve the NOx conversion, the catalyst that exhibited the best reduction of NOx was promoted by alkaline letals. Cs and Na showed a promoting effect while K displayed an inhibotory effect. Finally, an introduction to soot oxidation and the simultaneous elimination of propylene and NOx in the presence of soot was conducted. Another part of this work concerned atmospheric particles collected in Lebanon during dust-rich days originating from the Arabian Desert. Transformations in the morphology and chemical composition of aerosols were assessed by Scanning Electron Microscopy (SEM) equipped with an Energy Dispersive X-ray system. The results showed that coarse particles are rich in metal oxides (Si, Al, Mg, Fe, Ca...). However, over fine and ultrafine particles, the formation of organonitrates and organosulfates oligomers was observed. Yet, organonitrates sprung from the reaction between VOC and NOx.
164

Mixed metal oxide - noble metal catalysts for total oxidation of volatile organic compounds and carbon monoxide

Ferrandon, Magali January 2001 (has links)
CO, volatile organic compounds, and polyaromatics areubiquitous air pollutants that give rise to deleterious healthand environmental effects. Such compounds are emitted, forinstance, by the combustion of wood, particularly fromsmall-scale heating appliances. Total catalytic oxidation isconsidered to be an effective approach in controlling theseemissions, however, some problems remain such as thenon-availability of catalysts with low-cost, high activity andstability in prevailing conditions. Hence, this thesis aims atthe development of oxidation catalysts and improvedunderstanding of their behaviour. The catalytic activity was evaluated for the oxidation of amixture of CO, naphthalene (or ethylene), and methane inpresence of carbon dioxide, water, oxygen and nitrogen. Variouscharacterisation techniques, including Temperature-ProgrammedReduction and Oxidation, BET-Surface Area Analysis, X-RayDiffraction, X-Ray Photoelectron Spectroscopy, RamanSpectroscopy and Scanning and Transmission Electron Microscopywere used. In the first part of this thesis, catalysts based on metaloxides (MnOx, CuO) and/or a low amount of noble metals (Pt, Pd)supported on alumina washcoat were selected. It was shown thatPt and Pd possessed a superior catalytic activity to that ofCuO and MnOxfor the oxidation of CO, C10H8and C2H4, while for the oxidation of CH4, CuO was largely more active than noble metals,and MnOxas active as Pd and Pt. Some mixed metaloxide-noble metal catalysts showed decreased activity comparedto that of noble metals, however, a higher noble metal loadingor a successive impregnation with noble metals led to positivesynergetic effects for oxidation. Deactivation of the catalysts by thermal damage and sulphurpoisoning is addressed in the second part of the dissertation.An alumina washcoat was found to be well anchored to themetallic support after thermal treatment at 900°C due tothe growth of alumina whiskers. The sintering of the washcoatwas accelerated after high temperature treatments in thepresence of metal catalysts. In addition, alumina was found toreact with CuO, particularly in presence of noble metals at900°C, to form inactive CuAl2O4. However, MnOxcatalyst benefits from the more active Mn3O4phase at high temperature, which makes it asuitable active catalyst for the difficult oxidation of CH4. Pt sintering was delayed when mixed with CuO,thus giving more thermally resistant catalyst. The mixed metaloxide-noble metal catalysts showed higher activity afterpre-sulphation of the catalysts with 1000 ppm SO2in air at 600°C or during activitymeasurement in presence of 20 ppm SO2in the gas mixture, compared to single componentcatalysts. In some cases, the activities of the mixed catalystswere promoted by pre-sulphation due to the presence of sulphatespecies. Thermal stabilisation of the catalytic componentsand thealumina by promotion of La in the washcoat is discussed in thethird section. The stabilising effect of La at high temperatureis also compared to that of Ce added in the catalysts for otherpurposes. Due to its better dispersion, La contributed to thethermal stabilisation of the alumina washcoat and its activecomponents to a higher extent than Ce did. La provided a betterdispersion and a higher saturation of metal oxides in thealumina support, and at the same time stabilised the activityof the catalysts by preventing undesirable solid-phasereactions between metal oxide and alumina. In addition, La wasfound to enhance the dispersion and the oxygen mobility of CeO2. Cu-Ce interactions were found to promotesubstantially the CO oxidation due to an increase of thestability and reducibility of Cu species. Synergetic effectswere also found between Ce and La in the washcoat of CuO-Ptcatalyst, which facilitated the formation of reduced Pt and CeO2, thus enhancing significantly the catalyticactivity compared to that of a Pt only catalyst. The last part was an attempt to demonstrate the potential ofa catalyst equipped with a pre-heating device in a full-scalewood-fired boiler for minimising the high emissions during thestart-up phase. During the first ten minutes of the burningcycle a significant reduction of CO and hydrocarbons wereachieved. <b>Keywords</b>: wood combustion, catalysts, total oxidation,manganese, copper, platinum, palladium, lanthanum, cerium, CO,VOC, methane, deactivation, thermal stability, sulphurdioxide.
165

Development towards an efficient and sustainable biofuel drying

Bengtsson, Peter January 2009 (has links)
The usage of biofuel as well as wood fuel has increased in Sweden and all of Europe during recent decades, and there are several reasons to believe that this increase will continue. An important reason for this increase is that the environmental and climate problems caused by fossil fuels are becoming even more evident. By replacing fossil fuel with biofuel, the problem of emissions from, among others carbon dioxide and sulphur compounds can be alleviated. However, substitution requires in many cases high quality processed biofuel. An early stage in the processing of biofuel is drying. Previous work treats the possibility of drying wood fuel in an efficient and environmentally sustainable manner. This thesis studies the bed drying technique, conducted both experimentally and through modeling of the drying process. The experimental work is based on continuous temperature measurements in the fuel bed and provides characteristics of the drying zone that develops in the bed during drying. The character of the drying zone is affected by both the qualities of the fuel and the operating parameters, and is decisive regarding the possibility of making the drying more efficient, i.e. optimize the usage of energy and produce a fuel with low and homogeneous moisture content. A mathematical simulation model has been developed to increase the understanding of bed drying. The model is based on fundamental physical principles and is made up of five differential equations that describe vapor flow, air flow, the fuel’s moisture content, and the bed’s pressure and temperature. The modeling work complements the experimental work and a simulation of the temperature distribution, pressure and the drying zone’s dispersion is in agreement with the experimental result. The drying of wood can signify an environmental and human health risk, since volatile organic compounds (VOC) are emitted during drying. The thesis studies these emissions with regards to type and quantity. The measurements show that the majority of the emitted compounds from Norway spruce and Scots pine are volatile monoterpenes, but also that other compounds are emitted, especially higher terpenes. Further, major differences between how the compounds are emitted and the quantities of the emitted compounds from heartwood and sapwood are shown. There are also large differences between types of wood, i.e. spruce and pine. It can be stated that both emission rate and total amount of emitted compounds increase with an increase in temperature. To reduce VOC emissions, the drying temperature should be maintained low. To develop an efficient bed drying process for wood biofuels, additional parameters must be analyzed further and weighed against each other. Based on the experimental method and the simulation model presented here, the drying can be optimized towards a more efficient use of thermal energy and a low and even moisture content in the dried biofuel.
166

Utredning av potentiella hälsorisker i samband med slagg- och slaggvattenhantering vid Hedenverket, Karlstad / Study of Potential Health Risks in Connection with Handling of Bottom Ash and Bottom Ash Water at a Municipal Waste Incineration Plant

Eriksson, Jenny January 2004 (has links)
In this study potential health risks for employees in connection with handling of bottom ash and bottom ash water at a Municipal Waste Incineration (MWI) plant have been investigated. Air surrounding the bottom ash and the bottom ash water has been examined. MWI is one of the primary ways to manage solid household waste, and bottom ash is the main solid residue produced by the incineration process. Bottom ash constitutes about 15-20% of the original waste. The bottom ash is extinguished in a water bath (bottom ash water). The study was carried out in a MWI plant in Karlstad, Sweden. The plant is equipped with a grate furnace with a capacity of 7 tonnes per hour. Annually about 50 000 tonnes are incinerated at the plant. Levels of airborne particles, metals present in the airborne particles, volatile organic compounds (VOC), and phosphine were measured in the air. Analysis of the bottom ash water including: pH, total phosphorus, ammonium, chemical oxygen demand (COD), suspended solids, and bacteria were also carried out. Further, a questionnaire was distributed to investigate how the workers at the MWI plant re°ected on health when working. The results showed that the levels of airborne particles, metals and VOC did not pose any major health risks. The bacterial analysis demonstrated very low concentrations of bacteria in the water and thus that the bacteria posed no risk for the workers. The phosphine measurements did not result in levels exceeding the Swedish threshold limit value. However, the method used in this study was not well-tested in these sorts of environments and the results implied that higher levels of phosphine might be present. The conclusion from the questionnaire was that there is a concern about health risks in connection with certain tasks at the plant. / På Hedenverket, Karlstads Energi AB, förbränner man årligen cirka 50 000 ton hushålls- och verksamhetsavfall. En av restprodukterna av förbränningen kallas slagg (bottenaska) och utgör ca 15-20% av det inmatade avfallet. Slaggen släcks i ett vattenbad under själva pannan (slaggsläckningsbad) och matas sedan ut, via ett skakbord för reduktion av vatten, till containrar innan det slutligen körs på deponi. Syftet med det här projekt var att utreda om det föreligger några hälsorisker vid arbete kring slaggen och slaggsläckningsvattnet. För att skapa en bild av möjliga hälsorisker gjordes en inledande studie av tidigare utredningar, mätningar gjorda på avfallsförbränningsanläggningar runt om i Svergie och vad kemiska och biologiska hälsorisker innebär. Även lagstiftning på området har berörts. Med tidigare utredningar och mätningar samt diskussioner som grund utfördes mätningar av damm, metallhalter i damm, VOC och fosfin i luften samt en analys av slaggvattnet och bakterier i slaggvattnet. För att skapa en uppfattning av hur personalen, som arbetar med driften, upplever sin arbetssituation ur hälsorisksynpunkt genomfördes även en enkätundersökning. Resultaten av undersökningarna på Karlstads Energi AB visade att varken damm, metaller eller VOC utgör någon hälsorisk. Bakterieprovtagningen av slaggsläckningsvattnet visade på mycket låga halter av bakterier och bakterier kan därför inte sägas utgöra någon hälsorisk. Undersökningar av slaggvatten på andra anläggningar i Sverige visar däremot på höga metallhalter i slaggvattnet och det vore således inte särskilt hälsosamt att få i sig större mängder av detta. Resultaten av fosfinmätningen visar inte heller på några alarmerande nivåer, men metoden som användes är inte väl beprövad i den här typen av miljö. Resultaten kan tyda på att högre halter av fosfin förekommer, men hur höga de är inte möjligt att svara på. Fosfin är ett ämne som i små mängder kan ge upphov till bland annat illamående. I enkätundersökningen påtalades att obehag och illamående uppstºar vid längre arbeten över skakbordet och det är möjligt att fosfin kan vara en orsak till detta. Enkätundersökningen visade även att det finns en oro för hälsan vid vissa typer av arbeten på anläggningen och oro för att hälsan ska påverkas negativt på längre sikt.
167

Film Formation of Water-borne Polymer Dispersion: Designed Polymer Diffusion for High Performance Low VOC Emission Coatings

Soleimani Kheibari, Mohsen 31 August 2012 (has links)
In this thesis, I describe experiments that were designed to provide a better understanding of polymer diffusion during latex film formation. This step leads to the improvement of film mechanical properties. Polymer diffusion in these films was monitored by fluorescence resonance energy transfer. Current paint formulations contain Volatile Organic Compounds (VOCs) as plasticizers to facilitate polymer diffusion. The drawback of this technology is the release of VOCs to the atmosphere. VOCs are deleterious to the environment and contribute to smog and ground level ozone formation. The propensity of water, an indispensible part of any latex dispersion, to promote polymer diffusion was studied. Copolymers of poly (butyl acrylate-co-methyl methacrylate) and poly(ethylhexyl acrylate-co-tertiary butyl methacrylate) with similar glass transition temperatures but different hydrophobicity were compared. Polymer diffusion was monitored for films aged at different relative humidities. Water absorbed by the hydrophobic copolymer film was less efficient in promoting polymer diffusion than in the hydrophilic polymer. Only the fraction of water which is molecularly dissolved in the film participate actively in plasticization. Although water has low solubility in most latex polymers, molecularly dissolved water is more efficient than many traditional plasticizers. The possibility of modifying film formation behavior of acrylic dispersions with oligomers was studied by synthesizing hybrid polymer particles consisting of a high molecular weigh (high-M) polymer and an oligomer with the same composition. Oligomers with lower molecular weight are more efficient as diffusion promoters and have less deleterious effect on high-M polymer viscosity. A different set of hybrid particles were prepared in which the oligomer contained methacrylic acid units. The composition of the oligomer was tuned to be miscible with the high-M polymer when the acid groups were protonated but to phase separate when the acid groups were deprotonated. At basic pH, these particles adopt a core-shell morphology, with a shell rich in neutralized oligomers. After film formation, the oligomer shell retarded polymer diffusion. This retardation is expected to expand the time window during which the paint surface can be altered without leaving brush marks (open time). Short open time is a pressing problem in current technology.
168

Film Formation of Water-borne Polymer Dispersion: Designed Polymer Diffusion for High Performance Low VOC Emission Coatings

Soleimani Kheibari, Mohsen 31 August 2012 (has links)
In this thesis, I describe experiments that were designed to provide a better understanding of polymer diffusion during latex film formation. This step leads to the improvement of film mechanical properties. Polymer diffusion in these films was monitored by fluorescence resonance energy transfer. Current paint formulations contain Volatile Organic Compounds (VOCs) as plasticizers to facilitate polymer diffusion. The drawback of this technology is the release of VOCs to the atmosphere. VOCs are deleterious to the environment and contribute to smog and ground level ozone formation. The propensity of water, an indispensible part of any latex dispersion, to promote polymer diffusion was studied. Copolymers of poly (butyl acrylate-co-methyl methacrylate) and poly(ethylhexyl acrylate-co-tertiary butyl methacrylate) with similar glass transition temperatures but different hydrophobicity were compared. Polymer diffusion was monitored for films aged at different relative humidities. Water absorbed by the hydrophobic copolymer film was less efficient in promoting polymer diffusion than in the hydrophilic polymer. Only the fraction of water which is molecularly dissolved in the film participate actively in plasticization. Although water has low solubility in most latex polymers, molecularly dissolved water is more efficient than many traditional plasticizers. The possibility of modifying film formation behavior of acrylic dispersions with oligomers was studied by synthesizing hybrid polymer particles consisting of a high molecular weigh (high-M) polymer and an oligomer with the same composition. Oligomers with lower molecular weight are more efficient as diffusion promoters and have less deleterious effect on high-M polymer viscosity. A different set of hybrid particles were prepared in which the oligomer contained methacrylic acid units. The composition of the oligomer was tuned to be miscible with the high-M polymer when the acid groups were protonated but to phase separate when the acid groups were deprotonated. At basic pH, these particles adopt a core-shell morphology, with a shell rich in neutralized oligomers. After film formation, the oligomer shell retarded polymer diffusion. This retardation is expected to expand the time window during which the paint surface can be altered without leaving brush marks (open time). Short open time is a pressing problem in current technology.
169

The Study of Organic Solar Cell incorporating Bromined-P3HT¡JP3HT¡JPCBM as Active Layer

Chen, Deng-wei 18 August 2010 (has links)
Based on the solar cell¡¦s four characteristic parameter open-circuit voltage (Voc) makes the discussion.The study of the relation VOC¡¦s paper uses empirical formula. VOC¡¦s formula is ¡§VOC=(1/e)(¡UEDonorHOMO¡W-¡UEAcceptorLUMO¡W)-0.3V¡¨. We can know that VOC related to donor material¡¦s HOMO and acceptor material¡¦s LUMO, if we need a high VOC, it can change the structure of donor material to have higher HOMO value, as well as the acceptor material have lower LUMO value. Our active layer except poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-Butyric acid methyl ester (PCBM), the third material was blended to discuss their effect on the VOC. Two kind of different bromined-P3HT (Br-P3HT) were used 40% and 100% bromined-P3HT to blend in active layer. Their Three materials blended under the different weight percent and the basic device configurations in this study was ITO / PEDOT : PSS / P3HT : Br-P3HT : PCBM / Al , efficiency was measured under AM 1.5G 100mW/cm2 illumination. When blended Br-P3HT(100%) in the active layer, VOC increased from 0.6V to 0.68V and the surface roughness makes short-circuit current and fill factor, increased make lower power conversion efficiency. When blended Br-P3HT(40%) into the active layer, not only can increase VOC to 0.66V, but influence the short-circuit current and the fill factor. The power conversion efficiency changed from 2.20% to 2.46%.
170

Mixed metal oxide - noble metal catalysts for total oxidation of volatile organic compounds and carbon monoxide

Ferrandon, Magali January 2001 (has links)
<p>CO, volatile organic compounds, and polyaromatics areubiquitous air pollutants that give rise to deleterious healthand environmental effects. Such compounds are emitted, forinstance, by the combustion of wood, particularly fromsmall-scale heating appliances. Total catalytic oxidation isconsidered to be an effective approach in controlling theseemissions, however, some problems remain such as thenon-availability of catalysts with low-cost, high activity andstability in prevailing conditions. Hence, this thesis aims atthe development of oxidation catalysts and improvedunderstanding of their behaviour.</p><p>The catalytic activity was evaluated for the oxidation of amixture of CO, naphthalene (or ethylene), and methane inpresence of carbon dioxide, water, oxygen and nitrogen. Variouscharacterisation techniques, including Temperature-ProgrammedReduction and Oxidation, BET-Surface Area Analysis, X-RayDiffraction, X-Ray Photoelectron Spectroscopy, RamanSpectroscopy and Scanning and Transmission Electron Microscopywere used.</p><p>In the first part of this thesis, catalysts based on metaloxides (MnO<sub>x</sub>, CuO) and/or a low amount of noble metals (Pt, Pd)supported on alumina washcoat were selected. It was shown thatPt and Pd possessed a superior catalytic activity to that ofCuO and MnO<sub>x</sub>for the oxidation of CO, C<sub>10</sub>H<sub>8</sub>and C<sub>2</sub>H<sub>4</sub>, while for the oxidation of CH<sub>4</sub>, CuO was largely more active than noble metals,and MnO<sub>x</sub>as active as Pd and Pt. Some mixed metaloxide-noble metal catalysts showed decreased activity comparedto that of noble metals, however, a higher noble metal loadingor a successive impregnation with noble metals led to positivesynergetic effects for oxidation.</p><p>Deactivation of the catalysts by thermal damage and sulphurpoisoning is addressed in the second part of the dissertation.An alumina washcoat was found to be well anchored to themetallic support after thermal treatment at 900°C due tothe growth of alumina whiskers. The sintering of the washcoatwas accelerated after high temperature treatments in thepresence of metal catalysts. In addition, alumina was found toreact with CuO, particularly in presence of noble metals at900°C, to form inactive CuAl<sub>2</sub>O<sub>4</sub>. However, MnO<sub>x</sub>catalyst benefits from the more active Mn<sub>3</sub>O<sub>4</sub>phase at high temperature, which makes it asuitable active catalyst for the difficult oxidation of CH<sub>4</sub>. Pt sintering was delayed when mixed with CuO,thus giving more thermally resistant catalyst. The mixed metaloxide-noble metal catalysts showed higher activity afterpre-sulphation of the catalysts with 1000 ppm SO<sub>2</sub>in air at 600°C or during activitymeasurement in presence of 20 ppm SO<sub>2</sub>in the gas mixture, compared to single componentcatalysts. In some cases, the activities of the mixed catalystswere promoted by pre-sulphation due to the presence of sulphatespecies.</p><p>Thermal stabilisation of the catalytic componentsand thealumina by promotion of La in the washcoat is discussed in thethird section. The stabilising effect of La at high temperatureis also compared to that of Ce added in the catalysts for otherpurposes. Due to its better dispersion, La contributed to thethermal stabilisation of the alumina washcoat and its activecomponents to a higher extent than Ce did. La provided a betterdispersion and a higher saturation of metal oxides in thealumina support, and at the same time stabilised the activityof the catalysts by preventing undesirable solid-phasereactions between metal oxide and alumina. In addition, La wasfound to enhance the dispersion and the oxygen mobility of CeO<sub>2</sub>. Cu-Ce interactions were found to promotesubstantially the CO oxidation due to an increase of thestability and reducibility of Cu species. Synergetic effectswere also found between Ce and La in the washcoat of CuO-Ptcatalyst, which facilitated the formation of reduced Pt and CeO<sub>2</sub>, thus enhancing significantly the catalyticactivity compared to that of a Pt only catalyst.</p><p>The last part was an attempt to demonstrate the potential ofa catalyst equipped with a pre-heating device in a full-scalewood-fired boiler for minimising the high emissions during thestart-up phase. During the first ten minutes of the burningcycle a significant reduction of CO and hydrocarbons wereachieved.</p><p><b>Keywords</b>: wood combustion, catalysts, total oxidation,manganese, copper, platinum, palladium, lanthanum, cerium, CO,VOC, methane, deactivation, thermal stability, sulphurdioxide.</p>

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