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The aim of the present work was to experimentally investigate the influence of atomizing medium on combustion properties of methyl-ester of rapeseed oil. The experiments were carried out in a water-cooled horizontal combustion chamber. The pneumatic atomization using effervescent atomizer was used in test. As atomizing medium compressed air and superheated steam was chosen. The tests were performed at GLR = 15, 20 and 25 %. The experiments were focused on the investigation of the flame characteristics, quality of combustion, emissions, temperature of flue gas, distribution of heat fluxes and stability of combustion. Results revealed that atomization by compressed air is more efficient (approximately by 6 %), on the other hand it leads to higher NO emissions (for 15 mg/mN3 due to higher in-flame temperature).

This work begins with an introduction to catalysis focusing on heterogeneous systems and surface science phenomena. A study on the partial oxidation reaction of n-butane to maleic anhydride (MA) is presented in the first part. MA supplies are barely adequate for market requirements due to continued strong demand. Only slight improvement in catalytic performance would be welcome in the industrial community. The vanadium phosphorus oxide (VPO) catalyst was used in this work. The reaction is highly exothermic and the need to properly support the catalyst, not only for good dispersion but adequate heat dissipation is of crucial importance. For this, alpha-SiC commercial powders were used in synthesizing the catalyst due to its high thermal conductivity. Up to 25% MA yields were obtained and the reaction temperature was lowered by up to 28% using SiC/VPO mixed catalysts. The second part of this work is focused on the Fischer-Tropsch synthesis (FTS) process using cobalt silica supported catalysts. The main objective is the production of synthetic ultra high purity jet fuel (JP5). This is a very timely topic given the energy issues our world is facing. Almost all aspects of the FTS process have been extensively studied, however the effects of calcination temperature and silica support structure on the catalyst performance are lacking in literature. The catalysts were prepared using various silica supports. The catalysts had different drying and calcination temperatures. It was found that lower support surface area and calcination temperature catalysts exhibited higher activity due to lower support cobalt phase interaction. Co/silica catalysts calcined at 573K showed the highest CO conversion and the lowest CH4 selectivity. Catalysts prepared with 300m²/g support surface area exhibited 79.5% C5+ selectivity due to higher reducibility and less metal support interaction. The properties and performance of various prepared catalysts in both VPO and Co/silica systems are characterized by FTIR, XRD, BET, GC and XPS techniques. Theoretical FTS deactivation by sintering calculations and SiC/VPO particle temperature gradient calculations are presented as well. Finally, conclusions and future work on improving the yield and selectivity and scaling up the bench top setups are also presented.

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Philosophiae Doctor - PhD / The depletion of fossil fuel resources such as coal and the concern of climatic change arising from the emission of greenhouse gases (GHG) and global warming [1] lead to the identification of the 'hydrogen economy' as one of the renewable energy sources and possible futuristic energy conversion solution. Sources of hydrogen as fuel such as water through electrolysis and liquid organic fuel (Hydrogen carriers) have been found as potential game-changers and received increased attention, due to its low-carbon emission.

<p>Thermal, non-catalytic conversion of light olefins (C2= - C4=) was originally utilized in the production of motor fuels at several U.S. refineries in the 1920-30’s. However, the resulting fuels had relatively low-octane number and required harsh operating conditions (T > 450 oC, P > 50 bar), ultimately leading to its succession by solid acid catalytic processes. Despite the early utilization of the thermal reaction, relatively little is known about the reaction products, kinetics, and initiation pathway under liquid-producing conditions. </p> <p>In this thesis, thermal ethylene conversion was investigated near the industrial operating conditions, i.e, at temperatures between 320 and 500 oC and ethylene pressures from 1.5 to 43.5 bar. Non-oligomer products such as propylene and/or higher odd carbon products were observed at all reaction temperatures, pressures, and reaction extents. Methane and ethane were minor products (< 1 % each), even at ethylene conversions as high as 74 %. The isomer distributions revealed a preference for linear, terminal C4 and C5. The reaction order was found to be 2nd order with a temperature dependent activation energy ranging from 165 to 244 kJ/mol. The importance of diradical species in generating free radicals during a two-phase initiation process was proposed. The reaction chemistry for ethylene, which has only strong, vinyl C-H bonds starkly contrasted propylene, which possesses weaker allylic C-H bonds and showed preference for dimeric C6 products over C2-C8 non-oligomers. </p> <p>Extending this work further, the thermal oligomerization of ethylene was enhanced using high surface area supports such as silica and alumina. Both supports resulted in order of magnitude rate increases compared to the gas phase reaction, however the ethylene conversion rate with alumina was superior to silica by a factor of between 100 and 1,000. Additionally, the alumina evidently confers a catalytic function, resulting in altered product distributions, notably an increase in branched products such as isobutene and isopentenes. The oligomerization chemistry with alumina appears to reflect the involvement of Lewis acid sites rather than traditional Brønsted acid or transition metal catalysis, which operate via carbenium ion and metal-alkyl intermediates, respectively. </p>

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Thesis (MBA (Business Management))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The title of the study provides a summary of the content that is explored: The South African Liquid Fuels Market: Yesterday, Today and Tomorrow. A period spanning nearly 140 years is covered from 1882 to 2020. In “Yesterday”, the history of liquid fuels in South Africa is explored to understand the development of the liquid fuels market. The periods pre-1954, post-1954 and post-2003 are discussed. The period post-1954 is important due to the establishment of a highly developed crude oil refining and synthetic fuel production capability in South Africa. A section is also included to explain the international oil market because of the direct impact of crude oil and international oil prices on the South African liquid fuels market. “Today” explains the fuel price and demand and supply dynamics. The major role players in the liquid fuel market that shape the market are discussed. Government is actively involved in the market through the Department of Minerals and Energy and associated institutions, the CEF Group and Nersa. The South African Petroleum Association represents the seven largest oil companies in South Africa. An overview is provided of these seven companies and their operations in South Africa. In “Tomorrow”, international developments and domestic issues that will influence the liquid fuels market in the period 2010 to 2020 are identified. The future oil price and related issues of “peak oil” and fuel alternative vehicles have the ability to change the oil landscape dramatically. On the domestic side, the future petrol and diesel supply and demand balance are discussed in detail. The impact of the South African government on the market through clean fuel specifications and possible fuel price deregulation is also highlighted. It is clear from the study that historical as well as current supply and demand factors indicate that the South African liquid fuels market will continue to be a growth market that will be influenced by international oil market developments and domestic factors in the period 2010 to 2020. / AFRIKAANSE OPSOMMING: Die titel van die studie verskaf ‘n opsomming van die inhoud wat gedek word: Die Suid-Afrikaanse Brandstof Mark: Gister, Vandag en Môre. ‘n Periode van bykans 140 jaar word ondersoek wat strek vanaf 1882 tot 2020. “Gister” fokus op die geskiedenis van die brandstofmark in Suid-Afrika. Die periodes voor-1954, na-1954 en na-2003 word bespreek. In die periode na-1954 het Suid-Afrika ‘n indrukwekkende vermoë ontwikkel om ru-olie te raffineer en sintetiese brandstof te vervaardig. Die internasionale olie mark word ook bespreek as gevolg van die direkte impak wat ru-olie en internasionale olie pryse op die Suid-Afrikaanse brandstof mark het. “Vandag” verduidelik die brandstofprys asook vraag en aanbod faktore. Die belangrikste rolspelers wat die mark beinvloed word bespreek. Die regering is aktief betrokke in die mark deur die Deparment van Minerale en Energie en verwante organisasies, naamlik die CEF Groep en Nersa. Die Suid-Afrikaanse Branstofvereeniging verteenwoordig die sewe grootste olie maatskappye in Suid-Afrika. Die sewe maatskappye word bespreek en ‘n oorsig gegee oor hulle belange en bedrywighede in Suid-Afrika. In “Môre” word internasionale gebeure en plaaslike sake wat die brandstofmark in die periode 2010 tot 2020 kan beïnvloed ondersoek. Die toekomstige olie prys en verwante sake soos “spits olie” en voertuie wat van alternatiewe brandstof gebuik maak het die totale olie landskap verander. Op plaaslike vlak word die toekomstige petrol en diesel vraag en aanbod balans noukeurig ondersoek. Die Suid-Afrikaanse regering se impak deur skoon brandstof wetgewing en die moontlike de-regulering van die brandstofprys word beklemtoon. Die studie beklemtoon dat historiese asook huidige vraag en aanbod faktore daarop dui dat die Suid-Afrikaanse branstofmark steeds ‘n groeiende mark in die periode 2010 tot 2020 sal wees, wat beïnvloed sal word deur gebeure op die internasionale olie mark en plaaslike faktore.

Cette thèse s’articule autour de matériaux à base de bore pour des applications « énergie ». Nous avons développé deux classes de matériaux. (i) La première classe est dédiée au stockage chimique de l’hydrogène. Les matériaux étudiés dans cette partie sont produits par déstabilisation par mécanosynthèse de l’hydrazine borane N2H4BH3 en substituant un hydrogène protique de ce dernier par un cation alcalin. Nous avons particulièrement étudié la modification chimique de l’hydrazine borane par l’amidure de lithium LiNH2, puis par l’hydrure du calcium CaH2. Dans le premier cas, un nouveau composé de formule LiN2H3BH3.0,25NH3 a été obtenu. Dans le second cas, l’hydrazinidoborane de calcium Ca(N2H3BH3)2 a été synthétisé dans des conditions expérimentales spécifiques. (ii) La deuxième classe de matériaux concerne les polyboranes anioniques solubles dans l’eau pour une utilisation comme combustible anodique de pile à combustible liquide. Nous avons synthétisé et pleinement caractérisé le closo-décaborane de sodium Na2B10H10 et le 1-oxa-nido-dodécaborate de sodium NaB11H12O, puis leur électrooxydation a été étudiée et discutée sur différentes électrodes massives (platine, or et argent). Tous nos résultats sont présentés, discutés en détail et mis en perspective dans ce manuscrit de thèse. / The present work is structured around boron-based materials expected to be used in the field of “energy”. We especially worked on two types of materials. (i) With the first type, solid-state hydrogen storage was targeted. Hydrazine borane N2H4BH3 was used as precursor of novel derivatives obtained by mechanosynthesis. We first made it react with lithium amide LiNH2 to obtain LiN2H3BH3.0,25NH3. Then, we considered calcium hydride CaH2; it reacted with N2H4BH3 at 67°C (after ball-milling) to form a new phase, calcium hydrazinidoborane of formula Ca(N2H3BH3)2. (ii) The second type of boron-based materials we investigated is about anionic polyboranes. They are known to be stable in aqueous solution and accordingly could be used as anodic fuel of direct liquid-fed fuel cell. We aimed at synthesizing and fully characterizing two salts: sodium closo-decaborane Na2B10H10 and sodium 1-oxa-nido-dodecaborate NaB11H12O. Their potential for the aforementioned application was tested by cyclic voltammetry by using bulk electrodes of platinum, silver and gold. All of our results are presented, discussed in detail and put into perspective in the present thesis.