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Previous issue date: 2017 / Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM) / A crescente demanda global por combust?veis l?quidos para transporte, gera??o de eletricidade, atividade industrial e produ??o agropecu?ria tem imposto planejamento de a??es direcionadas ao uso de fontes ambientalmente limpas de energia. Os derivados da biomassa s?o alternativas econ?mica e tecnicamente vi?veis aos de origem f?ssil, n?o renov?vel, ora dominantes na matriz energ?tica global. O biodiesel, l?quido formado por uma mistura de ?steres de ?cidos graxos, ? adequado ? opera??o em motores de combust?o interna de ciclo Diesel, em substitui??o ou em complemento ao petrodiesel, ou em outras m?quinas t?rmicas. O prop?sito central do presente trabalho foi o desenvolvimento de um catalisador s?lido economicamente vi?vel, quimicamente eficiente e ambientalmente limpo para a produ??o de biodiesel via processos de transesterifica??o de triacilglicer?is dos ?leos de maca?ba ou de soja, com metanol. Foi preparado o catalisador heterog?neo baseado em iodeto de pot?ssio impregnado em s?lica amorfa (SiO2; derivada de areia da constru??o civil) e misturada a um componente magn?tico sint?tico (maghemita, ?Fe2O3). As estruturas qu?mica, cristalogr?fica e hiperfina essenciais e as propriedades magn?ticas dos materiais precursores e do catalisador s?lido foram investigadas. O teor de ?steres e a composi??o dos biodieseis produzidos foram determinados por cromatografia de fase gasosa acoplada a espectr?metro de massa. A composi??o qu?mica do catalisador, verificada por espectroscopias de energia dispersiva sob feixe de el?trons e por fluoresc?ncia de raios X (FRX), confirmou a ocorr?ncia de Si, Fe, K, e I. As ?reas espec?ficas BET encontradas para os componentes individuais, SiO2, ?Fe2O3 e do catalisador SiO2/KI/?Fe2O3, foram 352, 102, e 19 m2 g-1, respectivamente. A significativa redu??o da ?rea espec?fica do catalisador aponta que os componentes foram efetivamente impregnados no suporte. A morfologia das part?culas visualizadas por microscopias eletr?nicas de varredura e de transmiss?o revela a textura esponjosa do catalisador SiO2/KI/?Fe2O3, similarmente ao suporte de s?lica; o ?xido de ferro magn?tico aparece como material altamente organizado, cristalino, disperso no suporte. Os dados M?ssbauer e da magnetometria do ?xido de ferro magn?tico puro e no catalisador confirmam ser a maghemita, resultando em uma magnetiza??o de satura??o do catalisador de 4,6 emu g-1. O catalisador SiO2/KI/?Fe2O3, usado na transesterifica??o de triacilglicer?is, na propor??o em massa em rela??o ao ?leo da am?ndoa de maca?ba de 4,5% e raz?o molar ?leo:metanol de 1:35, levou ? produ??o de 94,3 massa% de ?steres, ap?s 8 h de rea??o. Foi experimentalmente observado que a maghemita tem comportamento qu?mico-catal?tico sin?rgico com os demais componentes do catalisador. O SiO2/KI/?Fe2O3 foi reutilizado em seis rea??es consecutivas com ?leo de soja, na mesma propor??o do catalisador e raz?o molar ?leo:metanol de 1:35, com rendimentos de 94,5% e tempo reacional de 110 min, para o primeiro ciclo, e de 61,2% e 150 min, para o ?ltimo ciclo. O catalisador, antes e ap?s cada ciclo de reuso, e as al?quotas das rea??es foram analisados por FRX, que mostrou que n?o h? perda significativa dos componentes do catalisador. Os resultados demonstram uma perspectiva tecnol?gica que permite redu??o substantiva do volume de efluentes poluentes e utiliza??o de diferentes mat?rias-primas oleaginosas de alto potencial para a produ??o de biodiesel. / Tese (Doutorado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / The global demand for liquid fuels destined to propel automobile motors and for all other types of transport has been growing significantly over the last decades in response to the needs of the population for mobility. These fuels are also necessary for the generation of electricity to support industrial and agricultural activities. However, the principal concern involved in the generation of mechanical work involves the threat that the effluents from burning fuels, particularly those from fossil origin, impart to the environment. Biomass-derived fuels are energetically, economically and environmentally interesting alternatives to the non-renewable fossil fuels, which still dominate the global energy matrix. Biodiesel, a liquid that is composed of a mixture of esters of fatty acids, is mainly suitable for use in Diesel-cycle internal combustion engines, totally replacing or partially complementing petrodiesel. The main purpose of the present work was the development of an economically viable, environmentally clean and chemically efficient solid catalyst for the production of biodiesel via the transesterification reaction of triacylglycerols from maca?ba or soybean oil with methanol. The proposed heterogeneous catalyst was based on potassium iodide-impregnated particles of amorphous silica (SiO2; derived from construction sand) mixed with a synthetic magnetic iron oxide (maghemite, ?Fe2O3). The essential chemical, crystallographic and hyperfine structures and magnetic properties of the starting materials and of the solid catalyst mixture were assessed by physical laboratory techniques. The ester content and the chemical composition of the biodiesel produced were determined by gas chromatography coupled with mass spectrometry. The chemical composition of the catalyst, as determined by electron energy dispersive and X-ray fluorescence (FRX) spectroscopies, confirmed the occurrence of Si, Fe, K, and I. Specific BET surface areas for the SiO2 and ?Fe2O3 components and for the SiO2/KI/?Fe2O3 catalyst were found to be 352; 102 and 19 m2 g-1, respectively. The significant reduction in the specific area of the catalyst indicates that the solid components were intimately mixed and that KI was indeed impregnated on the support. The morphology of the particles, as visualized from the scanning and transmission electron microscopy images, reveals the spongy texture of the SiO2/KI/?Fe2O3 catalyst, which was quite similar to that of the initial silica support. The atomic framework of the magnetic iron oxide appeared to be a highly organized, crystalline nano-material, relatively well dispersed on the silica support. The M?ssbauer and magnetometric data for the pure magnetic iron oxide and for the catalyst confirm that the component is essentially maghemite. The resulting saturation magnetization of the catalyst mixture was 4.6 emu g-1. From the chemical point of view, this maghemite was found to act synergically with the other components of the catalyst and to significantly improve its catalytic activity. The transesterification reaction of triacylglycerols using the SiO2/KI/?Fe2O3 catalyst at a mass ratio corresponding to 4.5 mass% relative to the maca?ba kernel oil and a methanol:oil molar ratio 30:1 yielded 94.3 mass% of esters after 8 h of reaction. The SiO2/KI/?Fe2O3 catalyst was reused for six consecutive transesterification reactions of triacylglicerols in soybean oil employing the same mass proportion of the catalyst and a methanol:oil molar ratio 35:1. A 94.5% yield of esters was obtained after 110 min of reaction in the first cycle, and a 61.2% yield was obtained in the last reaction cycle after 150 min. The compositions of the catalyst before and after each reaction cycle, along with detection of residual chemical elements in the liquid mixture of esters formed, were duly monitored by FRX. There was no significant leaching of the catalyst components during the reactions. These results open a perspective for (i) a substantial reduction in the volume of polluting effluents and (ii) the use bio-oils from native Brazilian flora (maca?ba) as raw materials for the industrial production of biodiesel.
| Identifer | oai:union.ndltd.org:IBICT/oai:acervo.ufvjm.edu.br/jspui:1/1527 |
| Date | 21 February 2017 |
| Creators | Macedo, Alice Lopes |
| Contributors | Fabris, Jos? Domingos, Roa, Juan Pedro Bretas, Cavalcante, Luis Carlos Duarte, Pasa, V?nya M?rcia Duarte, Verly, Rodrigo Moreira, Nelson, David Lee, Pereira, M?rcio C?sar, Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM), Fabris, Jos? Domingos |
| Publisher | UFVJM |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFVJM, instname:Universidade Federal dos Vales do Jequitinhonha e Mucuri, instacron:UFVJM |
| Rights | A concess?o da licen?a deste item refere-se ao ? termo de autoriza??o impresso assinado pelo autor, assim como na licen?a Creative Commons, com as seguintes condi??es: Na qualidade de titular dos direitos de autor da publica??o, autorizo a Universidade Federal dos Vales do Jequitinhonha e Mucuri e o IBICT a disponibilizar por meio de seus reposit?rios, sem ressarcimento dos direitos autorais, de acordo com a Lei n? 9610/98, o texto integral da obra disponibilizada, conforme permiss?es assinaladas, para fins de leitura, impress?o e/ou download, a t?tulo de divulga??o da produ??o cient?fica brasileira, e preserva??o, a partir desta data., info:eu-repo/semantics/openAccess |
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