Depuis quinze ans, de multiples instruments de mesure ont été envoyés vers Mars et explorent aujourd'hui sa surface ou y sont en orbite. Les données, renvoyées par ces sondes ont fourni une grande quantité d'informations quant aux conditions régnant aujourd'hui sur Mars, mais aussi sur la géologie des terrains et sur la minéralogie associée. Les minéraux découverts sur Mars se sont formés dans des conditions tout à fait différentes de celles qui y règnent aujourd'hui.Une approche associant modélisations numériques et expériences est proposée pour permettre d'identifier l'influence de divers processus comme le rayonnement UVC, la température et la pression partielle de CO2 ou de SO2. Des expériences en boîte à gants sont réalisées à des pressions partielles de CO2 de 10-6 bar, 10-3 bar et 10-2 bar, en présence ou non de rayonnement UVC. Conjointement à ces expériences, des expériences en capsules en or sont menées pour des températures de 20°C et 50°C avec des pressions partielles de CO2 d'environ 10-3 bar, 10-2 bar et 1 bar ainsi qu'avec une pression partielle de SO2 d'environ 1 bar. Les résultats ont montré qu'il était possible de reproduire expérimentalement et par les codes de calculs, la minéralogie supposée résultant de l'altération d'un verre basaltique de composition proche de roches martiennes. L'observation de carbonates de calcium dans les expériences réalisées à des pressions partielles de CO2 supérieures à 10-3 bar est en accord avec la prédiction de ces mêmes minéraux par des simulations numériques réalisées avec le logiciel DISSOL. Néanmoins, l'abondance de ces carbonates dans les deux types de modélisations, ainsi que leur composition à dominance calcique, contrastent avec les observations des rares minéraux carbonatés magnésiens à la surface de Mars. Ce contraste pose les questions concernant la composition de l'atmosphère, la composition initiale du verre et la préservation des carbonates après leur précipitation. Bien que des argiles n'aient pas été observées dans les expériences à cause d'un taux de dissolution du verre trop faible, des montmorillonites ferrifères et magnésiennes sont prédites dans les simulations numériques quelle que soit la pression partielle de CO2. De la beidellite sodique est également prédite dans le cas où les conditions atmosphériques martiennes seraient réductrices quelle que soit la pression partielle de CO2. Contrairement aux observations de la surface de Mars, aucune nontronite ne précipite. Les sulfates sont absents des paragenèses minérales obtenues lors des expériences avec une atmosphère à CO2. Dans les modélisations, aucun minéral sulfaté n'est néoformé pour les pressions partielles de CO2 imposées (> 10-6 bar) et la teneur en soufre du verre expérimental de synthèse. Toutefois, la précipitation de gypse peut être observée dans les simulations si la teneur en soufre est 100 fois supérieure à celle du verre utilisé pour ce travail. L'absence de sulfates magnésiens, de même que de carbonates magnésiens suggère que la composition chimique choisie pour le verre soumis à l'altération ne correspond pas totalement celle de la roche qui a pu donner les différents assemblages minéralogiques observés à la surface de Mars. En revanche, des sulfates de calcium et, des sulfates de fer et d'aluminium sont observés pour des expériences en capsules avec une atmosphère à SO2. Le rôle des atmosphères est essentiel quant à l'abondance des minéraux carbonatés et des minéraux sulfatés. Les expériences montrent que les radiations UVC accélèrent la dissolution du verre et favorise l'oxydation partielle du soufre du verre en pyrite / Process of deterioration on the primitive surface of Mars: experimental and digital simulations and mineralogical implications

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-06-15T16:12:16Z No. of bitstreams: 1 Jaqueline Ramos Grabasck_.pdf: 5267584 bytes, checksum: 3825ecf690630d4c9e3ed363b7a4647d (MD5) / Made available in DSpace on 2016-06-15T16:12:16Z (GMT). No. of bitstreams: 1 Jaqueline Ramos Grabasck_.pdf: 5267584 bytes, checksum: 3825ecf690630d4c9e3ed363b7a4647d (MD5) Previous issue date: 2016-03-31 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / FAPERGS - Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul / Os altos índices de consumo de recursos naturais e a geração de resíduos contribuem para os altos impactos ambientais da indústria da construção civil. A utilização de agregado reciclado a partir do beneficiamento dos resíduos de construção e demolição (RCD), embora seja fortemente incentivada pela legislação brasileira, ainda é incipiente. Porém, tanto o processo de extração de areia quanto o de beneficiamento de resíduos geram impactos ambientais e devem seguir uma série de legislações e limites de diferentes aspectos.Neste contexto, o objetivo deste trabalho consiste em analisar aspectos e impactos ambientais decorrentes da extração de areia natural e do beneficiamento do agregado reciclado de resíduos de construção e demolição. A primeira etapa da pesquisa consistiu em localizar as jazidas de extração de areia e as usinas de reciclagem de resíduos de construção e demolição, em âmbito nacional, por meio de pesquisas bibliográficas, sites do Governo e de organizações. Na segunda etapa da pesquisa, para realizar as avaliações de significância de aspectos e impactos ambientais foram visitadosdois empreendimentos, uma usina de reciclagem de RCD na Mesorregião Metropolitana de Porto Alegre e uma jazida de extração de areia na Mesorregião Centro Oriental Rio-Grandense. Ambos os processos apresentaram impactos com classificação crítica, ou seja, que acarretam em danos irreversíveis ao meio ambiente. Para averiguar a classe de risco na qual a qualidade do ar se enquadra, foram realizadas medições de concentrações de material particulado e determinada a taxa de sulfatação, sendo que apenas a emissão de material particulado apresentou valores acima dos estabelecidos pelas legislações vigentes. Por meio da quantificação do nível de pressão sonora, ficou evidente a necessidade de utilização de equipamentos de proteção individual (EPI’s) durante a operação da draga de extração e do britador. Os cálculos de emissões de CO2 indicaram que grandes deslocamentos fazem com que a utilização de areia natural extraída próxima ao consumo seja menos impactante do que o agregado reciclado, considerando a falta de usinas em todas as regiões. Entretanto, em locais que não há jazidas de areia natural, a instalação de usinas de reciclagem faz-se oportuna. / The high rates of natural resource consumption and waste generation contribute to the high environmental impacts of the construction industry. The use of recycled aggregate from Construction and Demolition Waste (CDW) processing, although it is strongly encouraged by Brazilian law it, is still incipient. However, either the sand mining process as waste processing generate environmental impacts and must follow a series of laws and limits of different aspects. In this context, the objective of this study wasto analyze the environmental aspects and impacts of natural sand extraction compared to the processing of recycled household waste from construction and demolition. The first stage of the research was to find the sand extraction mines and plants of recycling of waste from construction and demolition, nationwide, through literature searches, government sites and civil organizations. In the second stage of the research, to undertake the assessments of significance of environmental aspects and impacts two entreprises were visited, one construction and demolition waste (CDW) recycling plant in Metropolitan Porto Alegre and sand extraction quarry in Mesoregion East Center Rio Grande. Both processes presented critical impact rating, ie, which lead to irreversible damage to the environment. To determine the risk class in which the air quality falls, measurements were made of particulate matter concentrations and determined the sulfation rate. Only the emission of particulate matter presented values above established by current legislation. By quantifying the sound pressure level, it was evident the need for use of equipments for individual safety (EIF) during operation of the dredge mining and crusher. The calculation of CO2 emissions indicated that because of large displacements cause the next extracted using natural sand consumption is less harmful than the recycled aggregate, considering the lack of plants in all regions. However, in places where there is no natural sand deposits, the installation of recycling plants becomes urgent.

La gravure plasma de structures à fort rapport d'aspect dans le silicium est une étape clé dans la fabrication de microsystèmes et de composants de microélectronique de puissance. L'objectif de ce travail est de développer un procédé de gravure profonde du silicium, qui fonctionne à plus haute température de substrat que le procédé cryogénique en chimie plasma SF6/O2 et qui présente une meilleure stabilité en température et en concentration de gaz passivant(s). Dans ce but, de nouvelles voies de passivation non polymérisante ont été explorées. Nous avons évalué les possibilités de passivation par l'apport de SO2 en remplacement de O2. A température cryogénique, les propriétés de gravure sont semblables en plasma SF6/SO2 et SF6/O2 ; elles sont corrélées aux densités de neutres mesurées par spectrométrie de masse et actinométrie. La majeure partie des recherches a été consacrée à l'étude de la molécule SiCl4 comme précurseur de passivation. Nous avons au préalable analysé les interactions entre espèces générées en plasma SF6/SiCl4. Les expériences de caractérisation du plasma montrent que les réactions aux parois entre atomes F et espèces SiClx contrôlent la chimie du plasma et donc les propriétés de gravure du silicium. En mélange SF6/O2/SiCl4, ces réactions influent également sur la vitesse de gravure du substrat, mais l'ajout de SiCl4 à SF6/O2 a surtout pour effet de favoriser l'attaque chimique latérale. Nous avons finalement étudié la possibilité de former une couche de passivation par plasma SiCl4/O2 à température de substrat de -20 °C. Les résultats de cette étude permettent de proposer un nouveau procédé, basé sur l'alternance d'étapes de gravure par plasma SF6 et d'étapes de passivation par plasma SiCl4/O2.

Orientador: Arai Augusta Bernardez Pecora / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-11T13:29:17Z (GMT). No. of bitstreams: 1 Hory_RogerioIshikawa_D.pdf: 3549862 bytes, checksum: 727c6ab5dce7454b6af9546842232b2e (MD5) Previous issue date: 2007 / Resumo: Este trabalho apresenta o estudo experimental do processo de combustão de carvão mineral brasileiro em reator de Leito Fluidizado Circulante (LFC) com o objetivo de avaliar as taxas de emissões de di óxido de enxofre (S02) e eficiência de conversão de carbono no processo de combustão. Para diminuir a emissão do S02 nos gases de exaustão, foi adicionado, ao carvão, quantidades de calcário dolomítico (dolomita), de modo que a relação molar entre o cálcio (Ca) presente no calcário e o enxofre (S) presente no carvão variou entre 0,0 e 2,0. A variação na relação molar Ca/S, como é denominada na literatura, foi um dos dois fatores avaliados neste trabalho. O outro fator envolvido nos testes foi o excesso de ar utilizado para combustão do carvão. Trabalhou-se com excesso de ar na faixa de 20 a 30%. Foram realizados 11 ensaios seguindo um planejamento experimental estatístico do tipo CCD (Composite Central Design) e mais 02 ensaios complementares. A relação molar Ca/S de 0,6 apresentou emissão zero de S02 e propôs-se utilizar uma nova relação molar: (Ca+Mg)/S para retratar processos de sorção com dolomitas. Para emissão zero de S02, uma relação molar (Ca+Mg)/S de 1,8 já é suficiente. Foram obtidas eficiências de conversão do carbono entre 86,0 e 93,0% para combustão do carvão / Abstract: This work presents an experimental study with Brazilian mineral coal combustion in a Circulating Fluidized Bed (CFB) reactor with the objective to evaluate the sulphur dioxide emissions (S02) and the carbon conversion efficiency in the combustion processo Dolomite was added to the coal to minimize the S02 emissions during combustion. The quantity of dolomite added was calculated based on the molar relation of calcium (Ca) present in the dolomite and sulphur (S) present in the coal. Ca/S molar relation had a variation between 0,0 and 2,0. Two factors were evaluated in this work: Ca/S relation and excess of air during combustion which had a variation between 20 and 30%. Eleven (11) experimental tests were evaluated following a statistical experimental design called CCD (Composite Central Design) and 02 (two) more complementary tests. Emissions of S02 with zero value were obtained for a Ca/S of 0,6. It was also proposed in this work a new relation for sorption of S02 with dolomite: (Ca+Mg)/S relation. Tests showed that a relation of 1.8 for (Ca+Mg)/S is sufficient for zero emissions of S02. Carbon conversion efficiency between 86.0 and 93.0 was also obtained during coal combustion / Doutorado / Termica e Fluidos / Mestre em Engenharia Mecânica

L'état viable mais non cultivable (VNC) a été étudiée en détail chez les bactéries. En revanche,l'état VNC chez d'autres micro-organismes, y compris en particulier les eucaryotes, a reçubeaucoup moins d'attention.Pour fournir des preuves concluantes de l'existence d'un état VNC chez la levure, en particulierchez S. cerevisiae, la capacité des différentes souches de S. cerevisiae à devenir viable et noncultivable après un stress sulfite avec différentes concentrations de SO2 a été étudiée parcytométrie de flux (CMF) en utilisant une sonde fluorescente comme un marqueur de viabilité(fluorescéine diacétate (FDA)) et par étalement sur milieu de culture. La capacité des cellules àrécupérer leur cultivabilité après l’élimination du stress en augmentant le pH du milieu a étéétudiée. Pour confirmer l’existence de l'état VNC, le temps de génération de cellules VNC aprèsl’élimination du stress a été comparé aux cellules cultivables et viables dans des conditions deculture identiques. En outre, la comparaison des différentes phases du cycle cellulaire descellules sortent de l'état VNC et les cellules en état VNC a été réalisée par CMF. Par ailleurs,l'implication du gène SSU1 codant pour la pompe SO2 dans l'état VBNC a été étudiée.Après l'application du stress, la comparaison entre la population cultivable déterminée sur milieude culture et la population viable évaluée par FCM met en évidence la présence de cellulesviables mais non cultivables. L'augmentation du pH du milieu permet aux cellules de S.cerevisiae viables mais non cultivables à redeviennent cultivables. Le temps de génération, decellules cultivées dans les mêmes conditions que celles rencontrées au moment de la sortie del’état VNC, est comparé au temps de sortie calculé au cours de la reprise de la cultivabilité. Ladifférence entre ces deux paramètres observés affirme que le temps mis par les cellules poursortir de l’état VNC n’était pas caractéristique d’une multiplication cellulaire.Finalement nous avons étudié l'implication du SSU1 dans l'état VNC. Les résultats montrent quele SSU1 n’est pas impliqué dans le maintien de l'état VNC chez S. cerevisiae / The viable but not culturable (VBNC) state has been studied in detail in bacteria. Bycontrast the VBNC state in other microorganisms, including particularly eukaryotes, has receivedmuch less attention. However, it has been suggested that in wine, Brettanomyces yeast cells mayenter a Viable But Not Culturable State, in particular in the presence of high, sulfur dioxide(SO2) concentration.To provide conclusive evidences for the existence of a VBNC state in yeast, especially in S.cerevisiae as a model organism, the capacity of different S cerevisiae strains to become viableand not cultivable after a sulfite stress with various concentrations of SO2 was studied by flowcytometry (FCM) using fluorescent probe as a viability marker (Fluorescein diacetate (FDA))and by plating on culture medium. The ability of cells to recover cultivability after stress removalby increasing the pH medium was investigated. To confirm the VBNC state, the rate ofgeneration of VBNC cells after stress removal was compared to cultivable and viable cells insame culture conditions. In addition, the comparison of different cell cycle phases of cells exitingthe VBNC state and cells in VBNC state was performed by FMC. Moreover, the involvement ofSSU1 gene coding for the SO2 pump in VBNC state was studied.After stress application, comparison between cultivable population determined on culturemedium and viable population assessed by FCM demonstrated the presence of the viable cellswhich became uncultivable after 24 to 48 hours depending on the strains under study. Increasingthe pH medium allows the viable but uncultivable S. cerevisiae cells to become cultivable again.The generation rate of cells exiting VBNC state was not consistent with growth of residualculturable cells, which support a true VBNC state. The absence of cell proliferation, the stabilityof the population during the increase of the cultivability and the decrease in esterase activity forVBNC cells allows us to conclude the presence of the VBNC state in S. cerevisiae in correlationwith the VBNC state definition.In order to determine whether SSU1 gene, encoding a sulfite pump efflux, was involved inVBNC, we compare a wild type S. cerevisiae strain to its nul mutant Δ ssu1. Our resultsdemonstrate that SSU1 gene does not seem to be involved in VBNC phenotype

La molécule SO2 est connue depuis longtemps dans la pour son spectre d'absorption compliqué résultant de forts couplages entre les états électroniques impliqués. Cette longue histoire a récemment été complétée par de nouvelles études spectroscopiques résolues en temps; la spectroscopie de photoémission (TRPES) et la génération d'harmoniques d'ordre élevé. De nouvelles questions ont ainsi émergées, concernant le rôle des différents états électroniques excités, les différents couplages et leur temps caractéristiques. Pour répondre à ces questions, nous avons considéré, dans un premier temps, l'état électronique fondamental et les deux premiers états singulets excités. Ceux-ci interagissent par l'intermédiaire de couplage non-adiabatic, conduisant à la complexité du spectre d'absorption. Nos résultats se sont avérés particulièrement précis, en particulier pour la description des bandes de Cléments, donnant lieu à leur première description et interprétation théorique. Le couplage spin-orbite et les états triplets ont été introduits dans la description du système et l'analyse de la dynamique a permis de comprendre les différents mécanismes de conversion intersystème. Trois résultats majeurs sont obtenus, (i) le rôle prédominant d'un état 3B2, (ii) la présence d'interférences quantiques lors du processus et (iii) une nouvelle interprétation de la bande dite " interdite ", émanant des état triplets. Les spectroscopies TRPES et HHG ont été utilisées pour sonder la dynamique moléculaire dans ces états. Grâce à des simulations ab-initio nous montrons que la méthode TRPES permet l'étude la dynamique pour tous les états alors que la HHG n'est sensible qu'à la conversion intersystème. / The SO2 molecule is long known in the literature for its complex UV absorption spectrum, which is caused by a variety of strong couplings between the electronic states involved. This long and rich history was augmented recently by new time-dependent spectroscopic methods, namely, Time-Resolved Photoelectron Spectroscopy (TRPES) and High-order Harmonic Generation (HHG). Additional open questions emerged immediately, e.g., what was the role of the different known electronic states, which were the relevant couplings and also the timescales of the different relevant processes.To resolve these issues theoretically, we start by considering the electronic ground state and the two lowest singlet excited states. The latter interact through non-adiabatic couplings leading to a complex photoabsorption spectrum. Our results were accurate, especially concerning the Clements bands, and provide a comprehensive description of the photoabsorption spectrum. When including the spin-orbit coupling, relevant for the weak long-wavelength absorption system, the three-states model turns into a 12 coupled-states system. Analysis of the different couplings gives insight into the different mechanisms of the intersystem crossing. Three main points are shown: (i) the preponderant role of a 3B2 state, (ii) the possibility of quantum interferences during the process and (iii) a new interpretation of the forbidden band.The TRPES and the HHG spectroscopies have been used to probe the time-dependent dynamics in all these states. With the aid of first-principles simulations we show that the TRPES method is sensitive to the dynamics in the manifold, while HHG is sensitive only to the intersystem crossing.

An emission inventory tool for estimating SO2, NO2, and PM10 emissions from brick clamp kiln sites was developed from investigations performed on three representative South African clamp kiln sites in order to facilitate application for Atmospheric Emission Licenses (AELs) from these sources. The tool utilizes readily available site-specific parameters to generate emission factors for significant activities that emit the aforementioned pollutants. PM10 emission factors for significant processes were developed using empirical expressions from the Compilation of Air Pollutant Emission Factors (AP-42) documents. SO2 emission factor for clamp kiln firing was obtained from “reverse-modelling”, a technique that integrates ambient monitoring and dispersion modelling (using Atmospheric Dispersion Modelling System software) to “standardize” actual emission rate from an assumed rate of 1 g/s. The use of multiple point sources proved to improve the simulation of the buoyancy-induced plume rise; therefore, a “bi-point” source configuration was adopted for the kiln. The “reverse-modelling” technique and “bi-point” source configuration produced SO2 emission rates differing from -9 % to +22 % from mass balance results, indicating that the “reverse-modelling” calculations provide reliable emission estimates for SO2. An NO2 emission factor could not be obtained from the “reverse-modelling” technique due to experimental errors and the significant effect of NO2 emissions from other onsite air emission sources such as internal combustion engines. The NO2 emission factor was obtained from previous comprehensive study on a similar clamp kiln site. The emission factors obtained from this study were utilized in developing an “emission inventory tool” which is utilized by clay brick manufacturers in quantifying air emissions from their sites. Emissions quantification is a requirement for brick manufacturers to obtain an AEL which is regulated under South African environmental laws. It is suggested that the technique used here for SO2 emission confirmation could be used to estimate emissions from a volume or area source where combustion occurs and where knowledge of the source parameters is limited. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Chemical Engineering / unrestricted

Thesis (MSc. (Horticulture)) -- University of Limpopo, 2019 / After harvesting litchi fruit, the red pericarp colour is rapidly lost resulting in discolouration and browning during storage and marketing. To mitigate this challenge, the South African litchi industry uses sulfur dioxide fumigation to retain litchi fruit red pericarp colour during extended storage and shelf-life. However, there are health concerns regarding the commercially used (SO2) fumigation for litchi pericarp colour retention due to high levels of SO2 residues in fruit aril. Therefore, this study aimed to explore the possibility of Uvasys slow release SO2 sheets to retain ‘Mauritius’ litchi fruit red pericarp colour when packaged in plastic-punnets and bags. Treatment factors were two packaging materials (plastic-punnets and bags), six SO2 treatments (control; SO2 fumigation and four SO2 sheets viz. Uva-Uno-29% Na2S2O5; Dual-Release-Blue35.85% Na2S2O5; Slow-Release-36.5% Na2S2O5 and Dual-Release-Green-37.55% Na2S2O5) and four shelf-life periods (day 0, 1, 3 and 5). ‘Mauritius’ fruit were assessed for pericarp Browning Index (BI), Hue angle (ho), Chroma (C*) and Lightness (L*). In this study, an interactive significant effect (P < 0.05) between packaging type and SO2 treatments was observed on ‘Mauritius’ fruit pericarp L*, C* and ho during shelf-life. Fruit stored in plastic-bags and treated with SO2 fumigation showed higher pericarp C* and L*, while SO2 fumigated fruit in plastic-punnets had higher pericarp ho. Lower pericarp BI was observed in SO2 fumigated fruit stored in plastic-bags, which showed less pericarp browning than fruit in other treatments. In general, commercial SO2 fumigation resulted in lower pericarp BI, and higher pericarp L*, C* and ho throughout the storage and shelf-life. Our correlation analyses results further showed that litchi fruit red pericarp colour was better preserved as SO2 treatment levels increased, especially in plastic-bags. In retaining ‘Mauritius’ litchi fruit red pericarp colour, Uvasys SO2 sheets were not effective when compared with commercial SO2 fumigation. However, commercially SO2 fumigated fruit were bleached throughout the storage and shelf-life. Furthermore, fruit from all treatments were spoiled due to decay and mould growth after day 5 of shelf-life. Inclusion of pathogen protectants is important in future research to demonstrate whether Uvasys SO2 sheet-packaging technology can retain ‘Mauritius’ litchi fruit pericarp colour. / Agricultural Research Council and National Research Foundation (NRF)

Στην παρούσα διατριβή μελετήθηκε η μοριακή δομή και καταλυτική ενεργότητα καταλυτών V2O5/TiO2 και CrOx/TiO2 για την αντίδραση καταλυτικής αναγωγής των NO με χρήση NH3 (αντίδραση SCR) καθώς και καταλυτών V2O5-Cs2SO4/SiO2 (καταλύτες υγρής υποστηριγμένης φάσης) για την αντίδραση οξείδωσης του διοξειδίου του θείου. Η μελέτη της μοριακής δομής έγινε με χρήση in-situ φασματοσκοπία Raman υπό διάφορες αέριες συνθήκες (O2, NH3/N2, NH3/NO/N2, NH3/NO/O2/N2, 8% H2O/O2/N2, SO2/N2, SO2/O2/N2) και θερμοκρασίες. Γενικά σε χαμηλές φορτίσεις, σχηματίζονται αρχικά απομονωμένα τετραεδρικά βαναδικά (ή χρωμικά) είδη και αυξανόμενης της φόρτισης οδηγούμαστε στο σχηματισμό διμερών/ ολιμερών αλυσίδων. Η in-situ φασματοσκοπία ESR έδωσε συμπληρωματικές πληροφορίες για την μοριακή δομή των V4+, Cr5+ & Cr3+ ειδών, σε οξειδωτικές και αναγωγικές συνθήκες. Τέλος, η μελέτη της συμπεριφοράς της συχνότητας αναστροφής (TOF) στους καταλύτες βαναδίου έδειξε ότι η αντίδραση επιταχύνεται κατά την παρουσία γειτονικών κέντρων βαναδίου. Οι καταλύτες βαναδίου / καισίου είναι οι μοναδικοί στο είδος τους καταλύτες υποστηριγμένης υγρής φάσης, όπου σε συνθήκες αντίδρασης, η ενεργός φάση βρίσκεται υγρή ή διαλυμένη σε ένα μη πτητικό διάλυμα που “φιλοξενείται” στους πόρους του υποστρώματος. Η in-situ μελέτη Raman έδειξε ότι το ενεργό είδος για την καταλυτική οξείδωση του SO2 είναι τα βαναδικά οξοθειϊκά σύμπλοκα (VO)2O(SO4)44-. / In this ph.d. thesis, the molecular structure and catalytic reactivity of V2O5/TiO2 and CrOx/TiO2 catalysts was studied for the SCR reaction. Furthermore, the molecular structure of the unique SLP catalysts V2O5-Cs2SO4/SiO2 was studied for the reaction of the oxidation of SO2. This study was performed by the use of in-situ Raman spectroscopy in various “real” gas conditions (O2, NH3/N2, NH3/NO/N2, NH3/NO/O2/N2, 8% H2O/O2/N2, SO2/N2, SO2/O2/N2) and temperatures. In general, at low loadings isolated species are formed, and as the loading is increased, the formation of dimeric / oligomeric species is favoured. In situ ESR spectroscopy gave supplementary information about the structure of V4+, Cr5+ & Cr3+ species in oxidative / reductive environment. The behaviour of TOF numbers showed that the reaction is accelerated in the presence of neighbour vanadium centers (in case of vanadium catalysts). Finally, the vanadium / caesium catalysts are the unique in their kind molten salt catalysts, were in reaction conditions, the active phase is in liquid form or dissolved in a non-volatile solution which is “hosted” inside the pores of the support. Activation of these catalysts, following exposure to a SO2/O2/N2 mixture, results in uptake of SO3 and formation of a pyrosulfate molten salt which – as shown by in-situ Raman spectroscopy – vanadium occurs predominantly in the form if binuclear (VO)2O(SO4)44- which are considered to be the active species for the reaction.

Thesis (PhD)--Stellenbosch University, 2002 / ENGLISH ABSTRACT: Prototypes of a new polymer S02 gas-generating sheet for the control of Botrytis cinerea during the post-harvest storage of table grapes, were developed and manufactured for evaluation using a pilot scale production plant. Attention was paid to the appearance of the sheet, in order to make it technologically efficient as well as aesthetically acceptable to both industry and consumers. The storage quality of semi-commercial export consignments of various cultivars table grapes packed with the monolithic thin-film polymer S02 slow release sheet, was evaluated and compared to results obtained using the locally manufactured Uvasys S02 sheet. The following were investigated: the efficacy of the new polymer sheets in controlling storage decay, the stage at which S02 damage is manifested on table grapes, the level of S02 damage associated with different S02 concentrations, whether S02 damage is manifested more readily at a particular position on the bunch, and the possible effect of an increase in storage temperature, from an initial storage at -O.5°C to 10°C, on the levels of S02 bleaching. Results showed that the new polymer S02 sheet compared favourably with the existing, commercially available Uvasys S02 sheets. The exact S02 concentration required for effective decay control varied for different cultivars, as well as for the different types of grape packages. The S02 concentration incorporated within the sheet was shown to be lower for grapes packed in non-perforated bags, and slightly higher for those in perforated bags. Differences between cultivars occurred with regard to the level of control and the levels of S02 damage. Levels of S02 damage were also significantly affected by the storage period and temperature fluctuations. No significant differences in the levels of decay development and S02 damage were observed in relation to the orientation of the bunches in the carton. The extent of damage incurred to grape tissue by the absorption of S02 gas was determined by low-temperature scanning (LTSEM) and transmission electron microscopy (TEM) techniques. LTSEM and TEM micrographs of areas damaged by S02 gas revealed that exposure to S02 gas may lead to plasmolysis and the loss of cellular fluids. Although damage to the cell walls, cell wall structures and cell membranes, caused by S02 gas, was more prominent in the tissue layers nearer to the fruit surface, damage also occurred to a lesser extent in deeper tissue layers. S02 gas release-rate studies of polymer S02 sheets containing various concentrations Na2S205 revealed that levels of S02 gas emitted depended largely on the levels of Na2S205 incorporated into the sheets. Higher levels of S02 gas were released with the polymer sheets of higher concentrations Na2S205. The release curve for the commercial Uvasys S02 sheet was very different to that of the polymer sheets, with much higher levels of S02 gas emitted initially by the Uvasys S02 sheet compared to the polymer sheets, while the polymer sheets emitted low levels of S02 gas for longer periods compared to the Uvasys S02 sheet. The manufacturing process and the pilot scale production plant that was developed and constructed was successfully used to manufacture polymer S02 generating sheets that are technically sound and efficient, and aesthetically acceptable to industry. The efficacy of such sheets, regarding levels of decay control and S02 damage, was similar to that obtained with the presently available, commercially used Uvasys S02 sheet. / AFRIKAANSE OPSOMMING: 'n Nuwe polimeriese S02-gasvrystellingsvel vir die beheer van Botritis cinerea gedurende die na-oes opberging van tafeldruiwe is ontwikkel en vervaardig. 'n Nuwe loodsaanleg is spesiaal vir hierdie doel ontwerp en gebou. Aandag is geskenk aan die voorkoms van die velle aangesien dit belangrik is dat die nuwe velle beide tegnologies effektief en esteties aanvaarbaar moet wees vir die sagtevrugtebedryf en verbruikers. Die opbergingskwaliteit van semi-kommersiële uitvoerbesendings van verskeie kultivars tafeldruiwe, verpak met die nuwe monolitiese S02- gasvrystellingsvelle, is bepaal. Die volgende is ook bepaal: die effektiwiteit van die nuwe polimeriese velle, die stadium waarby S02-skade op die druiwe duidelik word, die vlak van S02-skade wat met verskillende konsentasies S02-gas geassosieer is, die moontlike invloed wat 'n toename in temperatuur (vanaf -0.5° tot 1DOC) op die verbleiking deur S02 sal hê, en of die S02-skade by voorkeur in 'n sekere posisie op die druiwe sal plaasvind. Die nuwe S02-vel het baie goed vergelyk met die kommersieël beskikbare Uvasys S02-vel. Die S02-konsentrasie benodig vir die effektiewe beheer van Botritis cinerea beskadiging het egter van kultivar tot kultivar verskil. Die keuse van die tipe verpakking, geperforeerd of ongeperforeerd, het ook 'n rol gespeel. Die konsentrasie S02-gas benodig vir effektiewe beheer was laer wanneer die druiwe in die nie-geperforeerde sakke verpak was. Vlakke van S02-skade is ook noemenswaardig beïnvloed deur die opbergingsperiode en variasies in temperatuur. Daar was geen duidelike verskil in die ontwikkeling van bederf en S02-skade ten opsigte van die posisie van die trosse in die karton nie. Die mate van S02-skade aan vrugweefsel is deur middel van laetemperatuurskandeerelektronmikroskopie (LTSEM) en transmissieelektronmikroskopie (TEM) bepaal. Daar is bevind dat die blootstelling aan S02 moontlik tot plasmolise en die uitlek van sellulêre vloeistof kon lei. Alhoewel S02-skade aan die selwande en membrane meer prominent in die weefsel naby die oppervlak van die vrug was, het skade ook in die onderliggende lae plaasgevind. Die vlakke van vrygestelde S02-gas het grootendeels afgehang van die konsentrasie natriummetabisulfiet in die velle. Die S02-vrystellingskurwe van die nuut ontwikkelde polimeriese S02-velle het baie verskil van dié van die Uvasys vel. Laasgenoemde lewer aanvanklik 'n hoë konsentrasie vrygestelde S02-gas vir 'n kort periode, gevolg deur baie lae S02 vlakke daarna, terwyl eersgenoemde 'n laer aanvanklike S02 vrystelling het, gevolg deur vergelykederwys hoër S02 konsentrasies daarna. Die ontwikkelde vervaardigingsproses en die loodsaanleg wat daaruit voortgevloei het is dus suksesvol aangewend om goeie polimeriese S02- vrystellingsvelle te vervaardig. Hierdie velle is tegnies effektief vir die beheer van Bofrifis cinerea gedurende die na-oes verpakking van tafeldruiwe en is esteties aanvaarbaar vir die Suid Afrikaanse sagtevrugtebedryf.