Heightened concerns for cleaner air and increasingly more stringent regulations on sulphur content in transportation fuels will make desulphurization more and more important. The sulphur problem is becoming more serious in general, particularly for diesel fuels as the regulated sulphur content is getting an order of magnitude lower, while the sulphur contents of crude oils are becoming higher. This thesis aimed to develop a desulphurisation process (based on oxidation followed by extraction) with high efficiency, selectivity and minimum energy consumption leading to minimum environmental impact via laboratory batch experiments, mathematical modelling and optimisation. Deep desulphurization of model sulphur compounds (di-n-butyl sulphide, dimethyl sulfoxide and dibenzothiophene) and heavy gas oils (HGO) derived from Libyan crude oil were conducted. A series of batch experiments were carried out using a small reactor operating at various temperatures (40 ¿ 100 0C) with hydrogen peroxide (H2O2) as oxidant and formic acid (HCOOH) as catalyst. Kinetic models for the oxidation process are then developed based on `total sulphur approach¿. Extraction of unoxidised and oxidised gas oils was also investigated using methanol, dimethylformamide (DMF) and N-methyl pyrolidone (NMP) as solvents. For each solvent, the `measures¿ such as: the partition coefficient (KP), effectiveness factor (Kf) and extractor factor (Ef) are used to select the best/effective solvent and to find the effective heavy gas oil/solvent ratios. A CSTR model is then developed for the process for evaluating viability of the large scale operation. It is noted that while the energy consumption and recovery issues could be ignored for batch experiments these could not be ignored for large scale operation. Large amount of heating is necessary even to carry out the reaction at 30-40 0C, the recovery of which is very important for maximising the profitability of operation and also to minimise environmental impact by reducing net CO2 release. Here the heat integration of the oxidation process is considered to recover most of the external energy input. However, this leads to putting a number of heat exchangers in the oxidation process requiring capital investment. Optimisation problem is formulated using gPROMS modelling tool to optimise some of the design and operating parameters (such as reaction temperature, residence time and splitter ratio) of integrated process while minimising an objective function which is a coupled function of capital and operating costs involving design and operating parameters. Two cases are studied: where (i) HGO and catalyst are fed as one feed stream and (ii) HGO and catalyst are treated as two feed streams. A liquid-liquid extraction model is then developed for the extraction of sulphur compounds from the oxidised heavy gas oil. With the experimentally determined KP multi stage liquid-liquid extraction process is modelled using gPROMS software and the process is simulated for three different solvents at different oil/solvent ratios to select the best solvent, and to obtain the best heavy gas oil to solvent ratio and number of extraction stages to reduce the sulphur content to less than 10 ppm. Finally, an integrated oxidation and extraction steps of ODS process is developed based on the batch experiments and modelling. The recovery of oxidant, catalyst and solvent are considered and preliminary economic analysis for the integrated ODS process is presented.

Die stöchiometrische Aktivierung von Trifluormethylschwefelpentafluorid mit dem Carben SIMes (1,3-Bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) wird thermisch und photochemisch beschrieben. Beide Formen der Aktivierung führen zur Detektion von 1,3-dimesityl-2,2-difluoroimidazolidin (SIMesF2), 1,3-dimesitylimidazolidin-2-sulfid (SIMes=S) und 1,3-dimesityl-2-fluoro-2-trifluoromethylimidazolidin (SIMes(CF3)F). Die Aktivierung von SF5CF3 wurde mit Radikalabfang-Experimenten untersucht, wobei die Ergebnisse auf die Bildung von CF3-Radikalen in der photochemischen Reaktion, nicht aber in der thermischen Reaktion hindeuten. Mechanistisch wird ein Einelektronentransfer von SIMes auf SF5CF3 postuliert. Weiterhin wurde die Reaktivität von SIMesF2 als Deoxyfluorierungsreagenz für verschiedene organische Substrate beobachtet. Zur mechanistischen Aufklärung der Acylfluorid-Synthese wurde das Imidazolidiniumsalz [SIMes-F]+F(HF)2- synthetisiert. Letzteres reagiert mit Benzoesäure zu Benzoylfluorid. Quantenmechanische Rechnungen bestätigen die These, dass ein externes Polyhydrogenfluorid für die Fluorierung der Benzoesäure verantwortlich ist. Anschließend wurde eine photoredoxkatalytische Trifluormethylierungen von Aromaten entwickelt. Ebenso wie bei der stöchiometrischen SF5CF3 Aktivierung wurde auch im Falle der photoredoxkatalytischen Aktivierung ein Einelektronentransfer auf SF5CF3 durch Oxidation des angeregten Katalysators oder Reduktion des zuvor oxidierten Katalysators vorgeschlagen. Experimentelle Untersuchungen des Mechanismus deuten auf die Entstehung von CF3-Radikalen, SF4 und Schwefel hin. Durch die Zugabe von Octanol zur Reaktionsmischung konnte die Bildung von Fluoroctan neben der Bildung von trifluormethylierten Aromaten erzielt werden. Dies deutet auf die Entstehung von Schwefeltetrafluorid hin und zeigt, dass SF5CF3 gleichzeitig als CF3-Quelle und als Quelle für SF4 dienen kann. / The stoichiometric activation of trifluoromethyl sulfur pentafluoride with the carbene SIMes (1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) is described thermally and photochemically. Both forms of activation lead to the detection of 1,3-dimesityl-2,2-difluoroimidazolidine (SIMesF2), 1,3-dimesitylimidazolidine-2-sulfide (SIMes=S) and 1,3-dimesityl-2-fluoro-2-trifluoromethylimidazolidine (SIMes(CF3)F). The activation of SF5CF3 was investigated by radical scavenging experiments, and the results indicate the formation of CF3 radicals in the photochemical reaction but not in the thermal reaction. Mechanistically, a one-electron transfer from SIMes to SF5CF3 is postulated. Furthermore, the reactivity of SIMesF2 as a deoxyfluorination reagent for several organic substrates was observed. The imidazolidinium salt [SIMes-F]+F(HF)2- was synthesized for the mechanistic investigation of the acyl fluoride synthesis. The latter reacts with benzoic acid to form benzoyl fluoride. Quantum mechanical calculations confirm that an external polyhydrogen fluoride is responsible for the fluorination of benzoic acid. Subsequently, a photoredox catalytic trifluoromethylation of aromatic compounds was developed. As in the case of stoichiometric SF5CF3 activation, a one-electron transfer to SF5CF3 by oxidation of the excited catalyst or reduction of the previously oxidized catalyst was also proposed in the case of photoredox catalytic activation. Experimental studies indicate the formation of CF3 radicals, SF4 and sulfur. The addition of octanol to the reaction mixture results in the formation of fluorooctane in addition to the formation of trifluoromethylated aromatics. This indicates the formation of sulfur tetrafluoride and shows that SF5CF3 can simultaneously serve as a CF3 source and as a source of SF4.

The world energy supply and demand, together with limited available resources have resulted in the need to develop alternative energy sources to ensure sustainable and expanding economies. Hydrogen is being considered a viable option with particular application to fuel cells. The Hybrid Sulphur cycle has been identified as a process to produce clean hydrogen (carbon free process) and can have economic benefits when coupled to nuclear reactors (High Temperature Gas Reactor) or solar heaters for the supply of the required process energy. The sulphur trioxide decomposition reactor producing sulphur dioxide for the electrolytic cells in a closed loop system has been examined, but it is clear that development with respect to a more durable active catalyst in a reactor operating under severe conditions needs to be investigated. A suitable sulphur trioxide reactor needs to operate at a high temperature with efficient heating in view of the endothermic reaction, and has to consist of special materials of construction to handle the very corrosive reactants and products. This investigation was undertaken to address (1) the synthesis, characterisation, reactivity and stability of a suitable catalyst (2), determination the reaction rate of the chosen catalyst with a suitable micro reactor (3) construction and evaluation of a packed bed reactor for the required reaction, and (4) the development and validation of a reactor model using computational fluid dynamics with associated chemical reactions. A supported catalyst consisting of 0.5 wt% platinum and 0.5 wt% palladium on rutile (TiO2, titania) was prepared by the sintering of an anatase/rutile supported catalyst with the same noble metal composition, synthesized according to an incipient impregnation procedure using cylindrical porous pellets (±1.7 mm diameter and ±5 mm long). Characterization involving: surface area, porosity, metal composition, - dispersion, - particle size, support phase and sulphur content was carried out and it was found from reactivity determinations that the sintered catalyst, which was very different from the synthesized catalyst, had an acceptable activity and stability which was suitable for further evaluation. A micro pellet reactor was constructed and operated and consisted of a small number of pellets (five) placed apart from each other in a two-stage quartz reactor with sulphur trioxide generated from sulphuric acid in the first stage and the conversion of sulphur trioxide in the second stage, respectively. Attention was only confined to the second stage involving the conversion of sulphur trioxide with the supported catalyst. The overall reaction kinetics of the pellets involving momentum, heat and mass transfer and chemical reaction was evaluated and validated with constants obtained from literature and with an unknown reaction rate equation for which constants were obtained by regression. As result of the complexity of the flow, mass and heat transfer fields in the micro pellet reactor it was necessary to use a CFD model with chemical reactions which was accomplished with a commercial code COMSOL MultiPhysics® 4.3b. A reversible reaction rate equation was used and a least squares regression procedure was used to evaluate the activation energy and pre-exponential factor. The activation energy obtained for the first order forward reaction was higher than values obtained from literature for a first order reaction rate (irreversible reaction) for the platinum group metals on titania catalysts. Detailed analyses of the velocity, temperature and concentration profile revealed the importance of using a complex model for determination of the reaction parameters. A fixed bed reactor system consisting of a sulphuric acid vaporizer, a single reactor tube (1 m length, 25 mm OD) heated with a surrounding electrical furnace followed, by a series of condensers for the analysis of the products was constructed and operated. Three process variables were investigated, which included the inlet temperature, the weight hourly velocity and the residence time in order to assess the performance of the reactor and generate results for developing a model. The results obtained included the wall and reactor centreline temperature profiles together with average conversion. As a result of the complexity of the chemistry and the phases present containing the products from the reactor a detailed calculation was done using vapour/liquid equilibrium with the accompanying mass balance (Aspen-Plus®) to determine the distribution of sulphur trioxide, sulphur dioxide, oxygen and steam. A mass balance was successfully completed with analyses including SO2 with a GC, O2 with a paramagnetic cell analyser, acid/base titrations with sodium hydroxide, SO2 titrations with iodine and measurement of condensables (mass and volume). The results obtained showed that a steady state (constant conversion) was obtained after approximately six hours and that it was possible to obtain sulphur trioxide conversion approaching equilibrium conditions for bed lengths of 100 mm with very low weight hourly space velocities. A heterogeneous 2D model consisting of the relevant continuity, momentum, heat transfer and mass transfer and the reaction rate equation determined in this investigation was developed and solved with the use of the commercial code COMSOL MultiPhysics® 4.3b with an appropriate mesh structure. The geometry of the packed bed (geometry) was accomplished by generating a randomly packed bed with a commercial package DigiPac™. The model predicted results that agreed with experimental results with conversions up to 56%, obtained over the following ranges: weight hourly space velocity equal to 15 h-1, temperatures between 903 K and 1053 K and residence times between 0.1 and 0.07 seconds. The post-processing results were most useful for assessing the effect of the controlling mechanisms and associated parameters. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2014

The world energy supply and demand, together with limited available resources have resulted in the need to develop alternative energy sources to ensure sustainable and expanding economies. Hydrogen is being considered a viable option with particular application to fuel cells. The Hybrid Sulphur cycle has been identified as a process to produce clean hydrogen (carbon free process) and can have economic benefits when coupled to nuclear reactors (High Temperature Gas Reactor) or solar heaters for the supply of the required process energy. The sulphur trioxide decomposition reactor producing sulphur dioxide for the electrolytic cells in a closed loop system has been examined, but it is clear that development with respect to a more durable active catalyst in a reactor operating under severe conditions needs to be investigated. A suitable sulphur trioxide reactor needs to operate at a high temperature with efficient heating in view of the endothermic reaction, and has to consist of special materials of construction to handle the very corrosive reactants and products. This investigation was undertaken to address (1) the synthesis, characterisation, reactivity and stability of a suitable catalyst (2), determination the reaction rate of the chosen catalyst with a suitable micro reactor (3) construction and evaluation of a packed bed reactor for the required reaction, and (4) the development and validation of a reactor model using computational fluid dynamics with associated chemical reactions. A supported catalyst consisting of 0.5 wt% platinum and 0.5 wt% palladium on rutile (TiO2, titania) was prepared by the sintering of an anatase/rutile supported catalyst with the same noble metal composition, synthesized according to an incipient impregnation procedure using cylindrical porous pellets (±1.7 mm diameter and ±5 mm long). Characterization involving: surface area, porosity, metal composition, - dispersion, - particle size, support phase and sulphur content was carried out and it was found from reactivity determinations that the sintered catalyst, which was very different from the synthesized catalyst, had an acceptable activity and stability which was suitable for further evaluation. A micro pellet reactor was constructed and operated and consisted of a small number of pellets (five) placed apart from each other in a two-stage quartz reactor with sulphur trioxide generated from sulphuric acid in the first stage and the conversion of sulphur trioxide in the second stage, respectively. Attention was only confined to the second stage involving the conversion of sulphur trioxide with the supported catalyst. The overall reaction kinetics of the pellets involving momentum, heat and mass transfer and chemical reaction was evaluated and validated with constants obtained from literature and with an unknown reaction rate equation for which constants were obtained by regression. As result of the complexity of the flow, mass and heat transfer fields in the micro pellet reactor it was necessary to use a CFD model with chemical reactions which was accomplished with a commercial code COMSOL MultiPhysics® 4.3b. A reversible reaction rate equation was used and a least squares regression procedure was used to evaluate the activation energy and pre-exponential factor. The activation energy obtained for the first order forward reaction was higher than values obtained from literature for a first order reaction rate (irreversible reaction) for the platinum group metals on titania catalysts. Detailed analyses of the velocity, temperature and concentration profile revealed the importance of using a complex model for determination of the reaction parameters. A fixed bed reactor system consisting of a sulphuric acid vaporizer, a single reactor tube (1 m length, 25 mm OD) heated with a surrounding electrical furnace followed, by a series of condensers for the analysis of the products was constructed and operated. Three process variables were investigated, which included the inlet temperature, the weight hourly velocity and the residence time in order to assess the performance of the reactor and generate results for developing a model. The results obtained included the wall and reactor centreline temperature profiles together with average conversion. As a result of the complexity of the chemistry and the phases present containing the products from the reactor a detailed calculation was done using vapour/liquid equilibrium with the accompanying mass balance (Aspen-Plus®) to determine the distribution of sulphur trioxide, sulphur dioxide, oxygen and steam. A mass balance was successfully completed with analyses including SO2 with a GC, O2 with a paramagnetic cell analyser, acid/base titrations with sodium hydroxide, SO2 titrations with iodine and measurement of condensables (mass and volume). The results obtained showed that a steady state (constant conversion) was obtained after approximately six hours and that it was possible to obtain sulphur trioxide conversion approaching equilibrium conditions for bed lengths of 100 mm with very low weight hourly space velocities. A heterogeneous 2D model consisting of the relevant continuity, momentum, heat transfer and mass transfer and the reaction rate equation determined in this investigation was developed and solved with the use of the commercial code COMSOL MultiPhysics® 4.3b with an appropriate mesh structure. The geometry of the packed bed (geometry) was accomplished by generating a randomly packed bed with a commercial package DigiPac™. The model predicted results that agreed with experimental results with conversions up to 56%, obtained over the following ranges: weight hourly space velocity equal to 15 h-1, temperatures between 903 K and 1053 K and residence times between 0.1 and 0.07 seconds. The post-processing results were most useful for assessing the effect of the controlling mechanisms and associated parameters. / PhD (Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2011. / Includes bibliogaphy. / ENGLISH ABSTRACT: Sauvignon blanc wines have become increasingly popular in South Africa as it is a cultivar that can be easily manipulated in the vineyard and cellar to produce a range of wine styles. These wines are usually given aroma descriptors such as green pepper, grassy and asparagus; while other more tropical aromas include passion fruit and guava. These aromas are thought to be mainly caused by methoxypyrazines and volatile thiols. These compounds are known to be character impacting compounds of Sauvignon blanc and are present in the grapes in the aromatic form (methoxypyrazines) or as non‐aromatic precursors (thiols) that can be released by the yeast during fermentation. Other aroma compounds such as esters, higher alcohols, fatty acids and monoterpenes are compounds that could potentially influence the aroma bouquet of a wine significantly. These aroma compounds exist either as precursors in the grapes (monoterpenes) or arise due to yeast metabolism during fermentation (esters, higher alcohols, fatty acids) and often display fruity, floral and pleasant aromas. In the cellar, winemaking practices can be manipulated to a certain extent to achieve the desired wine style. Winemaking tools such as temperature, skin contact, pressing conditions, oxygen (O2), sulphur dioxide (SO2) and yeast strain are only a few factors influencing the outcome of a wine. In general, South African winemakers maintain a very reductive environment during Sauvignon blanc wine production by using inert gasses, thereby causing the production costs to increase. There is sufficient evidence to support the reductive handling of white wine, however there seems to be a lack of information as to why the must should be treated reductively before fermentation. The over all goal of this study was thus to investigate the effect of different O2 and SO2 additions to Sauvignon blanc must before settling, specifically focussing on the typical aroma compounds often found in these wines. Chapter 2 gives an overview of the oxidation reactions occurring in must (enzymatic oxidation) and wine (chemical oxidation). This chapter also reports the origin of the specific Sauvignon blanc aroma compounds and their reaction to different must and wine treatments with a focus on oxidation. Chapter 3 reports research results focussing on the effect of the different must treatments on the character impacting compounds of Sauvignon blanc wines, specifically the methoxypyrazines and the volatile thiols. The effect of the treatments on the polyphenols and glutathione content in the must and wine was also investigated. Oxidation in the absence of SO2 led to a decrease in glutathione and certain phenolic compounds in the must. In general, volatile thiols were protected against oxidation by SO2, even when O2 was present in the must. Methoxypyrazines concentrations were not significantly influenced by the treatments. Chapter 4 elucidates the effect of the treatments on other yeast and grape derived aroma compounds often found in Sauvignon blanc wines, such as the esters, higher alcohols, fatty acids and monoterpenes. In general, the effect of SO2 seemed to have the greatest influence on the produced aroma compounds. The results reported in this thesis could possibly change the way South African Sauvignon blanc musts are handled in future during the winemaking process. It is clear that O2 and SO2 management in the cellar is of critical importance for the winemaker to produce wines of high quality. Future work is important to fully understand the mechanisms and evolution of important aroma compounds of Sauvignon blanc wines during the winemaking process. / AFRIKAANSE OPSOMMING: Sauvignon blanc wyn aroma word gewoonlik beskryf met terme soos groen rissie, grasagtig en aspersie terwyl ander tropiese aromas soos grenadella en koejawel ook dikwels voorkom. Die manipulasie van Sauvignon blanc in die wingerd en in die kelder tydens wynmaak, gee die wynprodusent die vryheid om ‘n wye reeks wyn style te produseer. Dit maak Sauvignon blanc baie populêr in die Suid‐Afrikaanse wynindustrie. Die bogenoemde aromas word waargeneem in die wyn as gevolg van die teenwoordigheid van sekere aroma komponente genaamd metoksipirasiene en vlugtige tiole. Hierdie komponente lewer ‘n unieke bydrae tot die aroma samestelling van Sauvignon blanc wyne en kom voor in die druiwe in die aromatiese vorm (metoksipirasiene) of as nie‐aromatiese voorlopers (tiole) wat tydens alkoholiese fermentasie deur die gis vrygestel kan word. Komponente soos esters, hoër alkohole, vetsure en monoterpene kan ook ‘n potensiële bydra lewer tot die algehele aroma van Sauvignon blanc wyne en kom voor in die druiwe (monoterpene) of ontstaan as gevolg van gis metabolisme gedurende alkoholiese fermentasie (esters, hoër alkohole, vetsure). Hierdie geur komponente word dikwels beskryf as vrugtig, blomagtig en oor die algemeen aangenaam. Tydens wynmaak kan die wyn tot ‘n mate gemanipuleer word om ‘n spesifieke wynstyl te bekom. Hulpmiddels soos temperatuur, dopkontak, pers omstandighede, suurstof (O2), swawel dioksied (SO2) en gisras is slegs ‘n paar faktore wat die algemene uitkoms van ‘n wyn kan beïnvloed. Oor die algemeen word Sauvignon blanc in Suid‐Afrika baie reduktief behandel tydens wynbereiding. Dit vereis sekere hulpmiddels, soos die gebruik van inerte gas, wat die produksiekoste dikwels verhoog. Navorsing ondersteun die reduktiewe behandeling van wit wyn, maar dit wil voorkom asof daar ‘n tekort aan navorsing is wat die reduktiewe behandeling van die sap voor fermentasie regverdig. Die algemene doel van die studie is dus om die effek van verskillende O2 en SO2 byvoegings tot Sauvignon blanc sap (voor afsak) te ondersoek met die fokus op die tipiese aroma komponente wat in die wyn voorkom. Hoofstuk 2 lewer ‘n algemene oorsig van die tipes oksidasie reaksies wat voorkom in sap (ensiematiese oksidasie) en wyn (chemiese oksidasie). Spesifieke Sauvignon blanc aroma komponente word ook ondersoek in terme van die oorsprong van die komponente asook die reaksie wat plaasvind met verskillende mos en wyn behandelings, met ‘n fokus op oksidasie. In hoofstuk 3 word die effek van die verskillende mos behandelings op tipiese Sauvignon blanc aroma komponente, spesifiek metoksipirasiene en vlugtige tiole, ondersoek. Die effek van die behandelings op die polifenole en glutatioon inhoud in die mos en wyn word ook gerapporteer. Oksidasie van die sap in die afwesigheid van SO2, het ‘n afname in glutatioon en sekere polifenol konsentrasies veroorsaak. Dit wil voorkom asof die produksie van vlugtige tiole oor die algemeen beskerm word teen oksidasie indien daar genoegsame SO2 teenwoordig is. Hierdie effek word ondervind selfs as die sap met suursof versadig word. Die effek van die behandelings op die konsentrasies van metoksipirasiene was nie beduidend nie. Hoofstuk 4 rapporteer die effek van die behandelings op ander aroma komponente soos esters, hoër alkohole, vetsure en monoterpene. Oor die algemeen wil dit voorkom asof die effek van SO2 beduidend was en waarskynlik die grootste invloed op die produksie van hierdie aroma komponente het. Na aanleiding van die resultate bevind in hierdie tesis, is daar ‘n moontlikheid dat die manier waarop Sauvignon blanc wyne geproduseer word in Suid‐Afrika, moontlik kan verander in die toekoms. Vir die wynmaker om hoë kwaliteit Sauvignon blanc wyne te produseer, is O2 en SO2 bestuur in die kelder van kardinale belang. Verdere navorsing moet steeds gedoen word om die meganisme en evolusie van belangrike aroma komponente in Sauvignon blanc wyne tydens die wynmaakproses, ten volle te verstaan.

Résumé du travail L’étude des modifications de surfaces, et plus particulièrement des matériaux d’électrodes est un domaine en plein essor. Les modifications d’électrodes par voie organique ont des applications potentielles dans des domaines aussi variés que l’inhibition de la corrosion, l’électronique moléculaire, l’optoélectronique ou encore les biosenseurs. Dans ce travail, nous nous sommes intéressés à l’électrode d’Au (111) modifiée par du 2-mercaptobenzimidazole. Dans un premier temps, l’adsorption du MBI sur électrode d’Au (111) sous contrôle du potentiel a été examinée par des mesures de capacité, de voltampérométrie cyclique, de chronocoulométrie et de spectroscopie SNIFTIR in situ. Les mesures de capacité révèlent qu’en milieu neutre, la molécule de MBI s’adsorbe en un film compact à des potentiels supérieurs à -0,3 V (vs. ECS). En deçà de cette valeur, le film se dilue progressivement lorsque le potentiel est rendu plus négatif, jusqu’à une valeur de -0,9 V où les molécules de MBI sont totalement désorbées de la surface. La morphologie des voltampérogrammes subit des variations significatives au cours du temps. Ces changements montrent que l’adsorption du MBI s’accompagne d’une levée de reconstruction de la surface, qui passe d’une structure initiale (√3 x 22) à une structure (1 x 1). Une estimation de la quantité de MBI adsorbée est obtenue par intégration des courbes de densité de courant. La courbe de densité de charge interfaciale a été extraite des mesures de chronocoulométrie. Cette courbe de densité de charge fournit des informations quant à l’évolution de l’excès superficiel en fonction du potentiel. La qualité des spectres infrarouges relevés in situ nous a permis d’effectuer des analyses qualitatives et quantitatives. Celles-ci montrent une bonne corrélation avec les résultats électrochimiques et apportent une signature moléculaire du film adsorbé et des espèces issues de sa désorption. Des calculs basés sur la Théorie de la Fonctionnelle de la Densité (DFT) ont permis une bonne interprétation des spectres infrarouges du MBI et de certains de ses dérivés. En outre, nous avons pu déterminer l’orientation des molécules à la surface, et montré que celle-ci varie peu avec le potentiel. Dans un second temps, nous nous sommes focalisés sur les propriétés de la monocouche auto-assemblée de MBI sur électrode d’Au (111), déterminées par voltampérométrie cyclique et spectroscopie infrarouge in situ. La monocouche est stable lorsque le potentiel est maintenu dans un domaine d’environ 800 mV. La monocouche auto-assemblée de MBI subit un processus de désorption réductive, influencé par le temps d’immersion de l’électrode dans la solution de surfactant ainsi que par le pH du milieu. Deux mécanismes de désorption réductive sont proposés, l’un valable en milieu neutre et basique, l’autre en milieu acide. Les résultats des mesures de spectroscopie infrarouge in situ apportent une preuve moléculaire de la validité des mécanismes proposés sur base des résultats électrochimiques. Un rapide examen des potentialités de cette monocouche a été réalisé à l’aide de réactions sondes. / Abstract Studies on surface modifications, and particularly of electrode material, are a growing field of interest. Organic modifications of electrode surfaces have potential applications in domains such as corrosion inhibition, molecular electronics, optoelectronics or biosensors. In the present work, we focussed on the modification of Au(111) electrodes by 2-mercaptobenzimidazole (MBI). In the first part, the adsorption, under potential control, of the MBI molecule onto the Au(111) electrode was studied by means of capacitance measurements, cyclic voltammetry, chronocoulometry and in-situ SNIFTIR spectroscopy. Capacitance measurements indicate that in neutral solution, the MBI molecule is adsorbed as a compact film at potentials higher than -0.3 V (vs. SCE). Below this value, the film becomes progressively less dense when the potential is made more negative, until a value of -0.9 V where MBI molecules are totally desorbed from the surface. The shape of the voltammograms evolves significantly with time. These changes show that a lift of the surface reconstruction occurs concomitantly to the adsorption of MBI. The initial (√3 x 22) reconstructed structure is lifted to the (1 x 1) unreconstructed one. The amount of adsorbed MBI is estimated by integration of the current density curves. The interfacial charge density curve was obtained by chronocoulometry measurements. This curve provides useful data regarding the evolution of the surface concentration with the potential. The quality of the infrared spectra obtained in situ allowed us to perform quantitative as well as qualitative analyses of the results. These analyses show a good correlation with the electrochemical results and provide molecular information on the adsorbed layer and on the species formed during the desorption process. Density Functional Theory (DFT) calculations were helpful in the interpretation of the infrared spectra of MBI and some of its derivatives. Additionally, we were able to determine the orientation of the molecules on the surface, and demonstrated that this orientation is slightly affected by the potential. In the second part of the work, we investigated the properties of the self-assembled monolayer of MBI on Au(111) electrode by cyclic voltammetry and in situ infrared spectroscopy. The monolayer is stable within an 800 mV potential range. The self-assembled monolayer undergoes a reductive desorption process, which is affected by the pH of the medium and by the immersion time of the electrode into the surfactant solution. Two mechanisms were proposed for the reductive desorption, one being valid in neutral and basic media, the other in acidic conditions. The in situ infrared spectroscopic results provide molecular evidences supporting the mechanisms proposed on an electrochemical basis. An exploratory examination of the potentialities of the monolayer is made by means of electrochemical probe reactions.

<p>The global oil refining industry with its present shift inproduct distribution towards fuels such as gasoline and dieselwill most likely hold the fort for many years to come. However,times will change and survival will very much depend onprocessing flexibility and being at the frontiers of refiningtechnology, a technology where catalysts play leading roles.Today oil refiners are faced with the challenge to producefuels that meet increasingly tight environmentalspecifications, in particular with respect to maximum sulphurcontent. At the same time, the quality of crude oil is becomingworse with higher amounts of polyaromatics, heteroatoms(sulphur and nitrogen) and heavy metals. In order to staycompetitive, it is desirable to upgrade dense streams withinthe refinery to value-added products. For example, upgradingthe fluid catalytic cracking (FCC) by-product light cycle oil(LCO) into a high quality diesel blending component is a veryattractive route and might involve a two-step catalyticprocess. In the first step the LCO is hydrotreated andheteroatoms are removed and polyaromatics are saturated, in thesecond step naphthenic rings are selectively opened to improvethe cetane number of the final product.</p><p>The present research is devoted to the second catalytic stepof LCO upgrading and was carried out within the framework of aEuropean Union project entitled RESCATS.</p><p>From the patent literature it is evident that iridium-basedcatalysts seem to be good candidates for ring-opening purposes.A literature survey covering ring opening of naphthenicmolecules shows the need for extending investigations toheavier model substances, more representative of the dieselfraction than model compounds such as alkylated mono C5 and C6-naphthenic rings frequently employed in academic studies.</p><p>Ring-opening catalysts, mainly Pt-Ir based, were synthesisedat KTH by two different methods: the microemulsion and theincipient wetness methods. Characterization of the catalystswas performed using a number of techniques including TPR,TEM-EDX, AFM and XPS etc. Catalytic screening at atmosphericpressure using pure indan as model substance was utilized todetect ring-opening activity and the magnitude of selectivityto desired cetane-boosting products. The development of suchring-opening catalysts is the topic of Paper I.</p><p>When designing a catalytic system aimed at refiningpetroleum, it is crucial to monitor the evolution of thesulphur distribution throughout the different stages of theprocess so that catalyst properties and reaction parameters canbe optimised. The final section of this thesis and Paper II arethus devoted to high-resolution sulphur distribution analysisby means of a sulphur chemiluminescence detector (SCD).</p><p><b>Keywords:</b>ring opening, naphthenes, cetane numberimprovement, indan, light cycle oil (LCO), Pt-Ir catalyst,catalyst characterization, aromatic sulphur compounds, GC-SCD,distribution, analysis.</p>

<p>This paper deals with the late Viking age/early medieval grave field in Björned, Torsåker parish, Ångermanland County in northern Sweden. The grave field in Björned is rare because it has all the signs of being Christianized before the surroundings. This awakes questions such as if the people of Björned came from another place and brought the religion with them or if someone else did that for them. To find these answers I have analysed the stable isotope ratios [delta]13C, [delta]15N and [delta]34S in human bone collagen. Through these stable isotopes we can not only see what the people consumed but also where their food had its origin. It seems like several people from the grave field had a different origin then the rest.</p>

L'activité volcanique peut représenter une source naturelle de pollution atmosphérique. Cette pollution peut engendrer une dégradation de la qualité de l'air, affecter la santé humaine et perturber la sécurité aérienne. Le Piton de la Fournaise à La Réunion est l'un des volcans basaltique les plus actifs au monde. Ses éruptions sporadiques génèrent des panaches volcaniques essentiellement constitués de gaz et de nanoparticules qui se propagent dans l'atmosphère. En journée, la formation d'oxydants (photolyse) permet d'oxyder une partie du dioxyde de soufre en acide sulfurique. Les molécules d'H2SO4 peuvent réagir avec les molécules d'eau atmosphérique pour former des embryons via la nucléation binaire homogène. Puis, ces embryons grossissent grâce aux processus de condensation et/ou coagulation conduisant alors à la formation d'un aérosol volcanique submicronique. Cette thèse vise à observer, comprendre et modéliser les processus de Formation de Nouvelles Particules (FNP) au sein des panaches volcaniques. De ce fait, elle s'organise en deux parties. La première se base sur les données recueillies lors de la campagne multidisciplinaire STRAP menée à l’observatoire du Maïdo et au Piton de la Fournaise en 2015. Elle expose les résultats issus d’une double analyse de la fréquence et de l’intensité des événements de FNP à l’observatoire. Tandis que la première analyse s’intéresse aux processus en l’absence du panache volcanique, la seconde met en exergue les spécificités de la FNP liées à sa présence au Maïdo. La seconde partie s'axe autour de la modélisation d'abord 0D puis 3D des processus de FNP au sein des panaches volcaniques via le modèle atmosphérique Méso-NH. / Volcanic activity can be a natural source of air pollution. This pollution can lead to a deterioration in air quality, affect human health and disrupt aviation safety. The Piton de la Fournaise in Reunion Island is one of the most active basaltic volcanoes in the world. Its sporadic eruptions generate volcanic plumes consisting mainly of gases and nanoparticles that spread in the atmosphere. During the day, a part of the sulphur dioxide can be oxidized to sulphuric acid thanks to oxidants production (photolysis). H2SO4molecules tend to react with atmospheric water molecules and form clusters via homogeneous binary nucleation. Then, these clusters grow by condensation and/or coagulation processes leading to the formation of a submicronic volcanic aerosol. This thesis aims to observe, understand and model the New Particle Formation (NPF) processes within volcanic plumes. Consequently, it is organized in two parts. The first is based on the data gathered during the multidisciplinary STRAP campaign conducted at both the Maïdo Observatory and Piton de la Fournaise volcano in 2015. It presents the results from a dual analysis of the NPF events frequency and intensity at the observatory. While the first analysis focuses on processes in the absence of the volcanic plume, the second highlights the specificities of the NPF related to the presence of the plume at Maïdo. The second part focuses on 0D then 3D NPF processes modelling within volcanic plumes via the Meso-NH atmospheric model.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science June 2015 / Lephalale is the home of Matimba, one of Eskom’s coal-fired power stations. Matimba is the biggest power station with a dry cooling system in the world. There are other industries (including coal mines) currently in operation in close proximity to the station. This industrial area is expected to grow as more industrial activities are planned for the following years. These activities will aggravate the levels of air pollution and possibly result in it being a “hot spot” for air pollution. The impact of air quality on health is covered by the National Ambient Air Quality Standards (NAAQS), but the impact of air quality on the terrestrial and aquatic ecosystem is not known. Therefore, this study focuses on the deposition of nitrogen oxides (NOx) (as nitrogen dioxide (NO2)) and sulphur dioxide (SO2) within Lephalale in the Waterberg-Bojanala Priority Area. Additionally, inter-annual variability of NOx and SO2 ambient concentrations and back trajectories of air masses were analysed. The study obtained ambient air quality data and meteorological data from Eskom for the period 2008–2012, while additional meteorological data were obtained from the Agricultural Research Council (ARC) and the South African Weather Service (SAWS). An inferential model was used to estimate the dry deposition flux of SO2 and NOx (as NO2), and the Hybrid Single Particle Langrangian Integrated Trajectory (Hysplit) Model was used to cluster back trajectories of air masses. The results of the seasonal dry deposition velocities of SO2 (0.17 to 0.23 cm/s) and NOx (0.10 to 0.15 cm/s) (as NO2) were higher in summer and lower in winter. They were also within the magnitude of the deposition velocities found in previous studies in the Highveld. The high deposition velocities in summer were attributed to photosynthetically active vegetation, turbulence and solar radiation. However, seasonal dry deposition fluxes of SO2 and NOx were higher in winter across the years. The higher flux values in winter were attributed to higher ambient concentrations of the trace gases. Additionally, the annual dry deposition flux of SO2 ranged between 0.43 and 0.67 kg S ha-1 yr-1, while NOx (as NO2) ranged between 0.84 and 1.05 kg N ha-1 yr-1 over the period studied. The annual deposition flux values found in the current study are lower than those found in previous studies in the Highveld. This difference could be because of the lower ambient concentrations of SO2 and NOx observed in this study. There is an inter-annual variability of the ambient concentrations of SO2 and NOx during the period 2008–2012. However, the difference is not large or statistically significant. The dominant direction of the back trajectories of air masses is east and southeast across all seasons for the entire period of 2008–2012. This lack of seasonal pattern in back trajectories and source regions cannot explain the seasonal changes in ambient concentrations (SO2 and NOx). Hence, climatic factors (e.g. change in weather) or seasonal changes in combustion source intensity must be responsible.