Thesis (Ph.D. (Natural and Agricultural Science)) -- University of Pretoria, 2009. / Includes bibliographical references.

Submitted in complete fulfilment for the Degree of Master of Technology: Biotechnology, Durban University of Technology, 2013. / The continual growth of the global biodiesel industry has resulted in a proportional increase in crude glycerol production. The by-production of glycerol waste during the manufacture of biodiesel has, with recent research, proven to hold use as a feedstock for the production of several commodity chemicals. The conversion of glycerol may be carried out by both chemical as well as biological means. The biological conversion of glycerol surpasses chemical conversion with respect to higher yield and selectivity, normal reaction conditions and the use of cheaper biological catalysts. Many microorganisms are known to convert glycerol to different value added products. This study involved the isolation of bacteria from soil and crude glycerol from a local biodiesel plant. Isolates were then used to convert crude glycerol supplemented with salts and a nitrogen source into commercially viable products. Isolates which successfully degraded glycerol were then identified via 16S PCR. A strain of Klebsiella pneumoniae, which is a known producer of 1,3-propanediol (1,3-PDO), was isolated from soil and two strains of Sphingomonas sp., which is a known gellan producer, was isolated from biodiesel waste. Gellan is an exopolysaccharide used in the food, cosmetic and pharmaceutical industries sold commercially as a product known as Gelrite or Gelzan while 1,3-PDO is an important component of fuels and polyesters (used widely in the petroleum industry) and is currently chemically produced. Using crude glycerol for producing 1,3-PDO is a good solution from an economic as well as ecological point of view. K. pneumoniae, Sphingomonas psueudosanguinis and Sphingomonas yabuuchiae were subjected to a series of shake flask fermentations in order to determine optimal growth conditions. This microoganism was able to successfully produce significant amounts of 1,3-PDO and lactic acid using crude glycerol (80 g/l), without pre-treatment (37 and 6.8 g/l respectively). S psueudosanguinis and S. yabuuchiae were both able to produce two of the highest amounts of gellan gum than that reported by other studies using crude glycerol (80 g/l) as a sole carbon source in a minimal medium (50.9 and 52.6 g/l respectively). / National Research Foundation

Made available in DSpace on 2014-06-11T19:25:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-24Bitstream added on 2014-06-13T19:53:28Z : No. of bitstreams: 1 pires_fi_me_araiq.pdf: 2131202 bytes, checksum: 4a1656266f5f8a9a0013485fdb7a1279 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A insuficiência do desempenho e estabilidade dos eletrocatalisadores são fatores que ainda inviabilizam o uso em larga escala das células a combustível de baixa temperatura de operação, tanto das PEMFC (“Polymer Electrolyte Membrane Fuel Cell”) quanto das DAFC (“Direct Alcohol Fuel Cell”), destacando-se as perdas associadas ao desempenho do catodo. Considerando a importância tecnológica de melhorar o desempenho das células a combustível, é evidente a necessidade de realizar estudos visando o desenvolvimento de eletrocatalisadores eficientes para a redução de oxigênio e tolerantes à presença de alcoóis. Além disso, desenvolver materiais alternativos que não contenham Pt é desejável para diminuir os custos dos catalisadores. A motivação geral deste trabalho foi a preparação e caracterização de nanopartículas bimetálicas PdM/C (M = Fe, Co e Ni) suportadas em carbono de elevada área superficial, com o intuito de estudar as suas propriedades eletrocatalíticas para a reação de redução de oxigênio, determinando também a estabilidade e a tolerância à presença de metanol, como estratégia para avaliar a viabilidade de que possam ser utilizadas como catodos em células a combustível. O trabalho envolveu a utilização do método do poliol para a obtenção dos eletrocatalisadores nanoparticulados bimetálicos a base de Pd, objetivando à obtenção de partículas com tamanhos inferiores a 8 nm e alta homogeneidade de tamanho e dispersão das partículas. O método de síntese foi utilizado variando-se o tempo de refluxo, sendo preparados catalisadores de PdNi/C, PdFe/C e PdCo/C com composições nominais 70:30 e 50:50. Nas condições testadas, foi possível a obtenção de ligas metálicas com tamanho de cristalito pequeno (em torno de 2nm). Os materiais preparados apresentaram boas... / The low performance and stability of the electrocatalysts are still factors that prevent the widespread use of fuel cells of low temperature operation, for the PEMFC (polymer electrolyte membrane fuel cell ) as well as for DAFC ( direct alcohol fuel cell), being the largest losses associated due to the performance of the cathode. Considering the technological importance of improving the fuel cells performance, it is evident that studies aiming the development of efficient electrocatalysts for oxygen reduction and tolerant of the presence of alcohols are needed. In addition, to develop Pt-free materials is desirable to reduce the cost of alternative catalysts. The purposes of this work were the preparation and characterization of bimetallic nanoparticles PdM/C (M = Fe, Co and Ni) supported on high surface area carbon, in order to study their electrocatalytic properties for the oxygen reduction reaction, measuring, as well, their stability and tolerance to the presence of methanol, as strategy to assess the viability of their use as fuel cells cathodes. The work involved the use of a polyol method to obtain the Pd-based bimetallic electrocatalysts, in order to obtain nanoparticles with sizes smaller than 8 nm, highly homogeneous in size and well dispersed on the support. The synthesis method was used varying the reflux time, for the preparation of PdNi/C, PdFe/C and PdCo/C catalysts with nominal compositions 70:30 and 50:50. Under those experimental conditions, it was possible to obtain alloys with small crystallite size (around 2 nm). The prepared materials showed good electrocatalytic properties for the oxygen reduction reaction. The accelerated tests of stability showed that the materials are stable, with durability superior to that of the commercial palladium catalyst used as reference material. The study of methanol tolerance showed that... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:35:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-18Bitstream added on 2014-06-13T19:25:05Z : No. of bitstreams: 1 moraes_jr_dr_guara.pdf: 858058 bytes, checksum: 9d3737c517e6bd0d7841460e47975a70 (MD5) / A crescente demanda por energia aumenta a busca por fontes energéticas alternativas a fim de se desvencilhar daquelas não renováveis. Todavia, a decisão por uma fonte energética leva em conta fatores técnicos, econômicos, sociais, políticos e ambientais. O termo biodiesel aplica-se ao combustível substituto do óleo diesel, constituído de ésteres obtidos a partir de óleos vegetais, por processo de transesterificação com álcoois em meio ácido ou básico. A utilização de óleos vegetais como combustível apresenta vantagens, principalmente, quanto às emissões de gases nocivos. Contudo, apresenta desvantagens como elevada viscosidade e falta de volatilidade, e seu processo de obtenção gera resíduo não totalmente aproveitável. Sistemas microemulsionados aparecem como um tipo de combustível alternativo, pois se ampliam os limites advindos das propriedades de cada componente da mistura. Pode-se intervir na redução das emissões de poluentes e também em suas características. Permite a utilização de substâncias com menor valor econômico e reaproveitamento de resíduos, constituindo-se como substitutos para os derivados de petróleo, propiciando autossuficiência energética, fortalecimento do agronegócio, desenvolvimento regional sustentável, geração de emprego/renda e melhoria da qualidade do ar / The growing demand for energy increases the search for alternatives to replace fossil sources by renewable energy sources. Nevertheless, the decision for an energy source shall consider technical factors, economic, social and environmental aspects as well. The term biodiesel refers to the substitute fuel for the original diesel, obtained from vegetable oil esters, by means of chemical transesterification with alcohols in acid or basic media. The use of vegetable oils as fuel presents many advantages, mainly concerning lower harmful gas emission. Although, they present disadvantages as high viscosity and lack of volatility, and their production process generates residues not completely usable. Micro-emulsion systems appear as alternatives because it is possible to take better advantage of the properties of each component of the system. It is possible to manipulate the system in order to reduce gas emissions and also their characteristics. It allows the use of components with lower economical value and recovery of residual products, becoming valuable substitutes for petrol derivatives, reducing external energy dependence, strengthen the agro-business, providing sustainable regional development, job and revenue generation and air quality improvement

Made available in DSpace on 2015-01-26T13:21:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-28Bitstream added on 2015-01-26T13:30:47Z : No. of bitstreams: 1 000802134.pdf: 2331571 bytes, checksum: 3098cbb9aa3c5c25a9cc346814de9c95 (MD5) / Na produção de biodiesel em pequena escala são comumente empregados os decantadores para separar o glicerol do biodiesel após a reação química de transesterificação do óleo com um álcool e um catalisador. Na maioria das vezes, esse processo de separação é realizado de forma manual e subjetiva por um operador que está sujeito a erros de interpretação, podendo, com isso, aumentar o custo de produção e/ou comprometer a qualidade do combustível produzido. Neste trabalho é proposta uma metodologia para o desenvolvimento e teste de um sistema eletrônico micro controlado, capaz de distinguir as fases formadas após o processo de decantação por meio de um sensor de condutividade elétrica, o qual permite o acionamento de válvulas para controle automático do direcionamento do biodiesel e do glicerol para reservatórios distintos. Essa metodologia contém a técnica de desenvolvimento abrangendo modelagem, simulação computacional, seleção de materiais, usinagem, projeto eletrônico, calibração e obtenção das características do desempenho do sensor. O sistema é composto por um painel elétrico que permite observar características do processo, através de um visor de LCD, e permite alterar as configurações do micro controlador, através da comunicação USB do equipamento com um computador. O sistema se mostrou eficiente nos testes com o biodiesel e glicerol, em processos produtivos com óleo de soja refinado, sendo que o glicerol apresentou valor de condutividade superior ao biodiesel, conforme esperado / In the production of biodiesel on a small scale decanters are commonly utilized to separate the glycerol from biodiesel produced after a chemical reaction of oil with some alcohol and a catalyst. In most cases, this separation process is done manually and subjectively by an operator that can make mistakes in interpretation, increasing the cost of production and/or compromising the quality of the fuel produced. This work presents a methodology for developing and testing of a micro controlled electronic system, capable of distinguishing the phases formed after the decanting process by means of an electrical conductivity sensor, which permits the actuation of valves in order to have an automatic control of the direction of biodiesel and glycerol for different reservoirs. This methodology contains the technical development including modeling, computer simulation, materials selection, manufacturing, electronic project, calibration and obtains the performance characteristics of the sensor. The system consists of an electrical panel, which allows to observe the process through features an LCD display and permits change the settings of microcontroller through the USB communication device with a computer. The system proved effective in tests with biodiesel and glycerol production processes with refined soybean oil, and glycerin showed conductivity value higher than biodiesel as expected

Made available in DSpace on 2018-07-27T18:26:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-05-06. Added 1 bitstream(s) on 2018-07-27T18:30:32Z : No. of bitstreams: 1 000870856.pdf: 2297678 bytes, checksum: 6aad44cf33b94a5bdcb65780e40fc4fe (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A modificação química do biodiesel tem sido uma proposta interessante para obtenção de diversos compostos oleoquímicos com propriedades e aplicações semelhantes aos derivados do petróleo, com o diferencial de serem obtidos através de rotas limpas e ambientalmente benigmas, utilizando insumos naturais como óleo vegetal e dióxido de carbono, atendendo diversos princípios da Química Verde. Este trabalho têm como proposta realizar uma série de modificações químicas do biodiesel de linhaça, partindo de sua síntese, epoxidação e cicloadição de CO2 para obtenção de epóxidos e carbonatos cíclicos biodegradáveis. O biodiesel de linhaça foi produzido através de catálise com ácido de Lewis (NbCl5) e teve seu teor de insaturação concentrado via purificação com uréia. A epoxidação do biodiesel concentrado teve sua cinética acompanhada pelo progresso do valor de oxigênio oxirano além de ser estudada via GC-FID e GC-MS. Os carbonatos cíclicos foram obtidos pela cicloadiação de CO2 supercrítico nos epóxidos catalisada por TEAB sem solvente e mostraram-se bons reagentes frente a diversas aminas para formação de carbamatos (uretanos). Espectros de FT-IR e RMN (1H e 13C) identificaram as transformações de todos os principais grupos funcionais comprovando êxito nas modificacões químicas propostas / The chemical modification of biodiesel has been an interesting proposal for obtaining various oleochemical compounds with similar porperties and aplications to petroleum derivates, with the difference of being obtained through clean and environmentally benign routes, using natural feedstock as vegetables oil and carbon dioxide, according to several principles of Green Chemistry. This work proposes to conduct a series of chemical modifications of flaxseed biodiesel, from its synthesis, epoxidation and cycloaddtion of CO2 to obtain biodegradable epoxides and cyclic carbonates. The flaxseed biodiesel was produced through Lewis acid catalysis (NbCl5) and had its unsaturation content concentrated by urea purification. The epoxidation of the concentrated biodiesel had its kinetics monitored by the evolution of oxygen oxirane value and studied by GC-FID and GC-MS. The cyclic carbonates were obtained from the solventless cycloaddition of supercritical CO2 in the opoxides catalyzed by TEAB, and have shown good reactants for a wide range of amines to from its respective carbamates (urethanes). FT-IR and NMR (1H and 13C) spectra identified the transformatios of all maior functional groups proving successful in the proposed chemical modifications

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