The manufacturing process for solventless extruded double base propellants involves a number of rolling and reworking stages. Throughout these processes a decrease in weight average molecular weight was observed, this was attributed to denitration. Differential scanning calorimetery data indicated that the reworking stages of extruded double base propellant manufacture were crucial to the homogenisation of the propellant mixture. To determine the homogeneity of the final extruded product, a sample was analysed across its diameter. No variations in stabiliser concentration, molecular weight, or Vickers hardness were detected. An accelerated thermal ageing trial simulating up to 8 years of ageing at 25°C was carried out to evaluate the storage characteristics. Reductions in stabiliser concentration, number average molecular weight, weight average molecular weight and polydispersity compared with un-aged samples were observed. The glass transition temperature measured using differential scanning calorimetery decreased by ~3°C. The decrease was attributed to the initial denitration reducing the energy of bond rotation and shortening the polymer chains, both factors reducing the energy required for movement. Modulus values determined from dynamic mechanical analysis temperature scanning experiments, did not detect significant variation between un-aged and aged samples. Though it was considered that variations would be likely if a more extensive ageing program was completed. In order to evaluate propellant behaviour at very high and low frequencies, time temperature superposition (TTS) and creep testing were carried out. The TTS technique superpositioned data well, allowing future investigation of high frequency propellant properties. Creep testing was considered to be an appropriate approach, though the equipment available was not optimised for such testing. This thesis is concerned with understanding how propellants are manufactured from nitrocellulose, nitroglycerine and other constituents. It is also about how the propellants decompose during long periods of time in storage, and how these changes can be measured using thermal and mechanical methods. It is about how the physical, chemical and thermal properties of the propellant composition change throughout the manufacture. This is relevant as it could be used to develop more efficient manufacturing processes, allow operators to adjust processes to tailor product properties or be used to re-design manufacturing to compensate for a different starting material. The thesis also considers how and why the properties of the product change over the course of years of storage. A specific focus on whether changes in mechanical and thermal properties occur, and if so how they can be detected. / © Cranfield University

>Magister Scientiae - MSc / Second generation biofuels production requires a suite of lignocellulolytic enzymes, acting synergistically to liberate the fermentable monosaccharides contained within agricultural waste materials. The use of thermostable lignocellulosic enzymes in a high-temperature process represents a number of advantages over their respective mesophilic counterparts, including increased solubility of the polymeric lignocellulosic substrates, enhanced enzyme processivity and reduced risk of bacterial and/or phage contamination during fermentation (Turner et al., 2007; Viikari et al., 2007). Alpha-L-arabinofuranosidases (AFases) participate in the deconstruction of lignocellulosic materials by hydrolysing the arabinofuranosyl bonds contained within the hemicellulosic portion of lignocellulose. In this study, three AFases isolated from compost-derived metagenomic DNA were characterised. Three genes derived from the fosmid metagenomic library constructed from 70°C compost were cloned into the pET21a(+) expression vector and expressed in E. coli BL21. The heterologously expressed proteins, AFase_H4, AFase_E3 and AFase_D3, were subsequently purified and their biochemical characteristics determined. All three AFases were shown to be active between pH 4.0 and 6.0. AFase_H4 and AFase_E3 displayed the highest activity at 60oC, while AFase_D3 had an optimum temperature at 25oC. Furthermore, the three AFases had differing thermostability profiles. In particular, AFase_E3 maintains 100% residual activity following 60 min incubation at 80oC and 24 hour incubation at 60oC. All three AFases have activity upon p-Nitrophenyl-arabinofuranoside and none against a range of alternative p-Nitrophenylglycosidic substrates. Phylogenetic analysis of the catalytic domain, identified within the amino acid sequences of the AFases, suggests that these AFases belong to glycoside hydrolase (GH) family 51. The difference in the AFase primary amino acid sequence motifs were used to infer differences in thermostability. All three AFases indicated similar biochemical and biophysical characteristics. AFase_E3 was determined to be the most thermostable amongst all three AFases. In the assessment of the three AFases respective suitability for inclusion in thermogenic bioethanol production processes, AFase_E3 was concluded as a suitable candidate for hydrolysis and synergistic testing on natural substrates. AFase_D3 possess the potential to be included in novel mesophilic industrialized process.

This diploma thesis deals with clean mobility, which becomes one of the current topics of today's society. Limited oil reserves and the state of the environment leads the goverments of developer countries to introduce alternative fuels in transport. The aim of the thesis is to clarify the economic costs and benefits of the practical application of clean mobility and to answer the question if the using of alternative fuels is economically rational. The Response is influenced by many factors and depends on the type of alternative fuel, the legislative framework of the country, the society awareness and others. Strength of the CNG's alternative fuel is mainly the lower fuel cost as well as for electromobility. The weakness of these fuels is the insufficient accessibility network of filling / charging places. An economic analysis of vehicle fleet modification of the Czech Environmental Inspectorate demonstrates that, under the current conditions, it is less costly to operate a vehicle with CNG alternative fuel. It is valid as well when the social cost of emissions are included.

The ternary phase behaviour of the n-heptane-l-propanol-water system was studied and compared with the theoretical prediction based on the UNIQUAC model for non-electrolyte solutions. The results showed that this model adequately approximated experimental studies. The excess enthalpies and excess volumes for several binary mixtures were determined. The excess enthalpies were measured using a LKB flow microcalorimeter and the excess -volumes determined using a PAAR densitometer. The study showed that no significant enthalpy or volume changes occurred when petrol/n-heptane were mixed with alcohols . Ternary phase diagrams, including tie lines have been determined for a number of petrol-alcohol-water systems (including the Sasol blend of alcohols). The tie line results show that the concentration of water in the water-rich layer is strongly dependent on the type of alcohol used. The Sasol alcohol blended with petrol resulted in a high water concentration in the water-rich layer which forms on phase separation. This is believed to contribute significantly to the corrosion problems experienced by motorists using the Sasol blended fuel on the Witwatersrand. The effect of temperature on several of these blends was included in the study. Diesel-alcohol blends and the co-solvent properties of ethyl acetate investigated. Ethyl acetate ensures miscibility at low concentrations for diesel-ethanol blends. Octyl nitrate and two cetane improvers from AECI were assessed in terms of their ability to restore cetane rating of blended diesel fuel to that of pure diesel fuel. The results indicated that all three samples were successful in this application. / KMBT_363

The production of biodiesel from vegetable oils is not a new technology; it has been around since the 1950’s and both the research in terms of the different feedstock that can be used and the production of biodiesel has since been gaining momentum as there needs to be a new, sustainable and domestic alternative to petroleum fuels. These petroleum fuels pose enormous threats to the environment and therefore need to be replaced as they are mostly contributing to climate change and global warming not to mention the frequent price hikes which are crippling the South African economy. Biodiesel production using vegetable oils seems to be and is the future and a law has recently been passed which sanctions the production of biofuel locally.[1] South African fuel producers will instigate obligatory blending of fossil fuel with biofuel as the country moves to encourage investment in its biofuels sector. The production of biodiesel locally and the blending of biodiesel with other petroleum products will reduce the country’s dependence on imported fuel. The already established petrochemical companies like BP, Sasol and Engine are therefore mandated to purchase these biofuels if and when the biofuels meet the required South African National Standard (SANS) 1935 requirements. This is then where the challenge comes as most of these growing biofuel companies cannot afford to purchase testing equipment.The growing companiesthen discover upon completion of the biofuel manufacturing process that their product does not meet the required standard specification. The failure translates to a financial loss as the final product can possibly not be reworked. The aim of the project is then to assist these companies who are manufacturing biofuel, by providing them with in-house biofuel process methods which will allow for early detection, should there be a need to redo a step in the process and not wait until the completion of the production process. These in-house process-testing methods will range from pH determination, titration tests which will determine the soap content and the percentage free fatty acid content, water determination, density and visual testing. It is not cost-effective for these biodiesel manufacturers to send their samples for outsource testing as evidently the results obtained would be out of specification hence the need to provide these biodiesel manufacturers with in-house analytical testing techniques that will aid in monitoring of the biodiesel production.

Biodiesel from microalgae is a viable alternative for replacing the global demand for petro-diesel. High biomass and lipid production are key desirable characteristics needed in a species to be used for biodiesel production. It has been demonstrated in literature that the increase in salinity can increase the lipid content of microalgae, but lower the growth rate of a species. Therefore the effect that salinity has on the growth and lipid content of ten microalgal species, isolated from a warm temperate solar saltworks, was investigated. The microalgae were cultivated at a temperature of 22°C and at salinities ranging from 17 to 70 psu. It was found that growth and lipid production for all species were influenced to some degree by the salinity. Growth rates greater than 0.6 d-1 showed a decrease with higher salinity. Most (71 percent) of the growth rates that exceeded 0.6 per day were exhibited by cultures exposed to normal salinity (35 psu). This shift is a good indication that salinity inhibits/slows down growth and that the species in general prefer lower salinity conditions. Growth rates ranged from 0.17 ± 0.05 to 1.19 ± 0.17 d-1. Lipid content for the diatoms (2.78 ± 0.36 to 10.86 ± 4.59 percent DW) were lower than expected, whereas the lipid content for the green flagellates (3.10 ± 1.56 to 22.64 ± 1.19 percent DW) was on par with that reported in literature. To bring results into perspective a production model was developed to simulate a production scenario at the Swartkops Saltworks. Lipid and productivity results obtained in this study were used to estimate how much oil and biomass can be produced within the ponds of the Swartkops Saltworks. The model showed that although microalgae cultivation for biodiesel is technically feasible, at present it is not economically viable to do so.

The diploma thesis focuses on world oil supply and aims to distinguish symptoms undoubtedly pointing to a possibly upcoming era of altered consumption and extraction patterns of oil products, which will be launched by "peak oil" -- a point when oil production reaches its maximum continues to decline. The thesis' objective is to analyse the probability of peak oil occurring and possible implications for world economy and selected countries. If proven true, it provides a an answer to the question whether the world economy can survive peaking without repercussions or whether it will shrink and decline into crisis. The first part defines the supply of oil and -- it's an overview of conventional and unconventional types of oil, petroleum products, oil fields, extraction techniques, energy effectiveness and substitutes. Furthermore, it defines "peak oil", it clarifies its history, strives to determine its possible date and compares it with the current oil situation. The second part surveys general implications of peak oil for world economics and politics -- it observes an unsatisfied oil demand, impact on the outputs of economies and the role of oil in economic crises. The political part follows with possible changes in the field of international politics. Lastly it tries to determine the effect on American suburbia. The third and final part is dedicated to selected countries, which are either important exporters or importers.

One of the leading problems that will be carried into the 21st century is that of alternative fuels to get our planet away from the consumption of fossil fuels. There has been a growing interest in the use of nanotechnology to somehow aid in this progression. There are several unanswered questions in how to do this. It is known that carbon nanotubes will store hydrogen but it is unclear how to increase that storage capacity and how to remove this hydrogen fuel once stored. This document offers some answers to these questions. It is possible to implant more hydrogen in a nanotube sample using a technique of ion implantation at energy levels ~50keV and below. This, accompanied with the rapid removal of that stored hydrogen through the application of a microwave field, proves to be one promising avenue to solve these two unanswered questions.

Solid phosphoric acid is a catalyst used for the upgrading of light olefins into fuels. To delve into the mechanism of olefin dimerisation over the catalyst, the oligomerisation of 1- hexene was investigated over a wide range of operating conditions. The reaction progression of 1-hexene dimerisation over solid phosphoric acid was interpreted by means of kinetic experiments for both a linear hexene (1-hexene) and a branched hexene (2,3-dimethylbutene). The reaction rate for both reagents was described by using an elementary kinetic model. From the experimental data it was shown that the rate of dimerisation of branched hexenes was faster than the rate observed for linear hexene dimerisation. To correlate the two sets of kinetic data, the reaction network was expanded to incorporate skeletal isomerisation of 1-hexene with dimerisation only taking place by the co-dimerisation of linear and branched hexenes and the dimerisation of branched hexenes. The fit of the kinetic equation demonstrated that the reaction rate of 1-hexene is essentially controlled by the rate of skeletal isomerisation. Due to the large activation energy for skeletal isomerisation, low reaction temperatures favoured the co-dimerisation of linear and branched hexenes whereas at higher temperatures, the reaction rate was dominated by the dimerisation of branched hexenes. The product distribution indicated that, because of the fast rates of both cracking and secondary dimerisation (dimerisation of cracked products), the product distribution instantaneously reached a pseudo equilibrium after the dimerisation of hexenes. Therefore the carbon distribution was found to depend only on the reaction temperature, not on the residence time in the reactor. Solid phosphoric acid is a supported liquid phosphoric acid where the condensed state of the acid, e.g. ortho phosphoric acid (H3PO4) and pyro phosphoric acid (H4P2O7), is dependent on the quantity of water present in the reaction mixture. With a decrease in water content, the distribution of acid shifts and the ortho phosphoric acid becomes more condensed (H4P2O7, H5P3O9 etc.), i.e. high water content → low acid strength, low water content → high acid strength. The experiments completed at various degrees of catalyst hydration and free acid loading showed that the rate of reaction over solid phosphoric acid was dependent on the acid strength of the catalyst. The effect of acid strength on the reaction rate was integrated into the rate constants by means of an exponential dependency on acid strength. It was also shown that both the product distribution and the degree of branching remained unaffected by acid strength. The constant product indicates that the rate of cracking is limited by the rate of oligomerisation of hexenes, irrespective of the acid strength of the catalyst. Since the product from the dimerisation of 1-hexene could be used as fuel, the quality of the desired fuel would therefore depend solely on the reaction temperature, not on the hydration of the catalyst. The work performed in this thesis has been published in two peer-review articles: 1. Schwarzer R.B., Du Toit E. and Nicol W. (2008) Kinetic model for the dimerisation of 1-hexene over a solid phosphoric acid catalyst, Applied Catalysis A: General, 340, 119-124. 2. Schwarzer R.B., Du Toit E. and Nicol W. (2009) Solid phosphoric acid catalysts: The effect of free acid composition on selectivity and activity for 1-hexene dimerisation, Applied Catalysis A: General, 369, 83-89. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Thesis (M. Sc. (Microbiology)) --University of Limpopo, 2017 / The recent oil crisis and environmental concerns over fossil fuels has led to the development of biofuels from lignocellulosic materials. Two main sugars from lignocellulose that can be used for bioethanol production are glucose and xylose. Xylose is problematic, because there are few yeasts that can utilise and ferment it. Xylose fermentation is not as efficient compared to glucose fermentation. Some of the factors that affect xylose fermentation include rate of xylose consumption, aeration, temperature and inhibitors. To improve ethanol production and fermentations and to make the process economically viable at industrial scale, there is a need to find a robust microorganism that can ferment efficiently in harsh industrial conditions. Therefore, the aim of this study was to investigate by means of evolutionary engineering (adaptation), the adaptability of seven locally isolated yeasts in terms of growth on high xylose concentration, in the presence of acetic acid as well as at elevated temperatures. Seven yeast strains (Candida guilliermondii MBI2, Candida sp. Kp6.2ey, Candida tropicalis Kp21ey, Candida tropicalis Kp42ey, Candida tropicalis Kp43ey, Ogatea methanolica Kp2ey and Pichia kudriavzevii Kp34ey) were adapted to ferment 60 g/L xylose as sole carbon source in the presence of 3 g/L acetic acid at 37°C. P. kudriavzevii Kp34ey was the only yeast to adapt to these conditions. The adapted P. kudriavzevii Kp34ey was compared with the parental strain (unadapted) and a reference strain, Scheffersomyces stipitis NRRLY-7124, using different volumetric oxygen transfer coefficient (KLa) rates. P. kudriavzevii Kp34ey (adapted and parental strain) and S. stipitis NRRLY-7124 produced the highest ethanol concentrations at a KLa value of 3.3. Overall, for all KLa values tested, the adapted strain performed better than the parental strain and S. stipitis NRRLY-7124. The adapted P. kudriavzevii Kp34ey yielded 4.03 g/L ethanol on 60 g/L xylose with 3 g/l acetic acid at 37°C at a KLa value of 3.3 and was the only yeast tested to grow under these conditions.