Made available in DSpace on 2014-12-17T15:42:06Z (GMT). No. of bitstreams: 1 AmandaDG.pdf: 3418517 bytes, checksum: 8b4c45093282af02fba617928f13a7de (MD5) Previous issue date: 2009-03-20 / Petr?leo Brasileiro SA - PETROBRAS / This work aims to study the effects of adding antioxidants, such as, α- tocopherol and BHT on the thermal and oxidative stability of biodiesel from cottonseed (B100). The Biodiesel was obtained through the methylical and ethylical routes. The main physical and chemical properties of cotton seed oil and the B100 were determined and characterized by FTIR and GC. The study of the efficiency of antioxidants, mentioned above, in concentrations of 200, 500, 1000, 1500, 2000ppm, to thermal and oxidative stability, was achieved by Thermogravimetry (TG), Differential Thermal Analysis (DTA), Differential Scanning Calorimetry (DSC), Differential Scanning Calorimetry - Hi-Pressure (P-DSC) and Rancimat. The Biodiesel obtained are within the specifications laid down by Resolution of ANP No7/2008. The results of TG curves show that the addition of both antioxidants, even in the lowest concentration, increases the thermal stability of Biodieseis. Through the DTA and DSC it was possible to study the physical and chemical transitions occurred in the process of volatilization and decomposition of the material under study. The initial time (OT) and temperature (Tp) of oxidation were determined through the P-DSC curve and they showed that the α-tocopherol has a pro-oxidant behavior for some high concentrations. The BHT showed better results than the α-tocopherol, with regard to the resistance to oxidation / Este trabalho tem como objetivo estudar o efeito da adi??o de agentes antioxidantes, tais como o α-tocoferol e BHT sobre a estabilidade t?rmica e oxidativa do biodiesel de algod?o (B100), obtido pelas rotas met?licas e et?licas. Foram determinadas as principais propriedades f?sico-qu?micas do ?leo de algod?o e do B100, al?m das caracteriza??es atrav?s de Espectroscopia de Absor??o na Regi?o de Infravermelho (FTIR) e Cromatografia Gasosa (CG). O estudo da efici?ncia dos antioxidantes adicionados, nas concentra??es de 200, 500, 1000, 1500 e 2000 ppm, para as estabilidades t?rmicas e oxidativa, foi realizado atrav?s da Termogravimetria (TG), An?lise T?rmica Diferencial (DTA), Calorimetria Explorat?ria Diferencial (DSC), Calorimetria Explorat?ria Diferencial sob Press?o (P-DSC) e Rancimat. As amostras de biodiesel apresentaram-se dentro das especifica??es estabelecidas pela Resolu??o da ANP No 7/2008. A adi??o de ambos os antioxidantes, mesmo em baixa concentra??o (200 ppm), aumentou a estabilidade t?rmica dos B100. Atrav?s das curvas DTA e DSC, foram estudadas as transi??es f?sico-qu?micas ocorridas no biodiesel. O tempo inicial (OIT) e temperatura (Tp) de oxida??o, determinados atrav?s das curvas P-DSC, mostraram que o α-tocoferol tem comportamento pr?-oxidante para algumas concentra??es elevadas. O BHT apresentou melhor resultado do que o α-tocoferol, com rela??o ? resist?ncia ? oxida??o

Made available in DSpace on 2014-12-17T15:42:20Z (GMT). No. of bitstreams: 1 HellydaKTAS_DISSERT.pdf: 3306619 bytes, checksum: 6db9524bb03341082d99032fc6dfcf10 (MD5) Previous issue date: 2011-03-11 / Biodiesel is a fuel made up by mono-alkyl-esters of long chain fatty acids, derived from vegetable oils or animal fat. This fuel can be used in compression ignition engines for automotive propulsion or energy generation, as a partial or total substitute of fossil diesel fuel. Biodiesel can be processed from different mechanisms. Transesterification is the most common process for obtaining biodiesel, in which an ester compound reacts with an alcohol to form a new ester and a new alcohol. These reactions are normally catalyzed by the addition of an acid or a base. Initially sunflower, castor and soybean oil physicochemical properties are determined according to standard test methods, to evaluate if they had favorable conditions for use as raw material in the transesterification reaction. Sunflower, castor and soybean biodiesel were obtained by the methylic transesterification route in the presence of KOH and presented a yield above 93% m/m. The sunflower/castor and soybean/castor blends were studied with the aim of evaluating the thermal and oxidative stability of the biofuels. The biodiesel and blends were characterized by acid value, iodine value, density, flash point, sulfur content, and content of methanol and esters by gas chromatography (GC). Also studies of thermal and oxidative stability by Thermogravimetry (TG), Differential Scanning Calorimetry High Pressure (P-DSC) and dynamic method exothermic and Rancimat were carried out. Biodiesel sunflower and soybean are presented according to the specifications established by the Resolution ANP no 7/2008. Biodiesel from castor oil, as expected, showed a high density and kinematic viscosity. For the blends studied, the concentration of castor biodiesel to increased the density, kinematic viscosity and flash point. The addition of castor biodiesel as antioxidant in sunflower and soybean biodiesels is promising, for a significant improvement in resistance to autoxidation and therefore on its oxidative stability. The blends showed that compliance with the requirements of the ANP have been included in the range of 20-40%. This form may be used as a partial substitute of fossil diesel / Biodiesel ? um combust?vel constitu?do por mono-alquil-?steres de ?cidos graxos de cadeias longas, derivado de ?leos vegetais ou gordura animal. Este combust?vel pode ser utilizado em motores de igni??o por compress?o para a propuls?o de ve?culos autom?veis ou gera??o de energia, como um substituto parcial ou total de diesel f?ssil combust?vel. O biodiesel pode ser processado a partir de diferentes mecanismos. A transesterifica??o ? o processo mais comum para obten??o do biodiesel, em que um ?ster reage com um ?lcool para formar outro ?ster e um novo ?lcool. Essas rea??es s?o normalmente catalisadas pela adi??o de um ?cido ou uma base. Inicialmente, foram determinadas as propriedades f?sico-qu?micas dos ?leos de girassol, mamona e soja de acordo com as especifica??es de metodologias de teste padronizadas, com o intuito de avaliar se os mesmos possu?am condi??es favor?veis para serem utilizados como mat?ria-prima na rea??o de transesterifica??o. O biodiesel desses ?leos foi obtido atrav?s da rea??o de transesterifica??o pela rota met?lica, fazendo uso de KOH no preparo do catalisador (met?xido de pot?ssio). O rendimento das rea??es de transesterifica??o foi acima de 93% m/m. Os biocombust?veis e as blends foram caracterizados pelos ?ndices de acidez e iodo, ponto de fulgor, pela massa espec?fica, pelos teores de enxofre, metanol e ?steres. As estabilidades t?rmica e oxidativa foram avaliadas atrav?s da Termogravimetria (TG), da Calorimetria Explorat?ria Diferencial sob Press?o (P-DSC) pelos m?todos din?mico e isot?rmico, e do Rancimat. As amostras de biodiesel de girassol e soja apresentaram conformidade com as especifica??es estabelecidas pela Resolu??o ANP no 7/2008. O biodiesel de mamona, como esperado, apresentou elevadas massa espec?fica e viscosidade cinem?tica. A adi??o do biodiesel de mamona como antioxidante ao biodiesel de girassol e de soja ? promissora, pois promoveu uma melhora significativa na resist?ncia ? auto-oxida??o e, por conseguinte, na estabilidade oxidativa de ambos. Para as blends estudadas, o aumento da concentra??o de biodiesel de mamona contribuiu para um aumento da massa espec?fica, viscosidade cinem?tica e ponto de fulgor. As blends que apresentaram conformidade ?s exig?ncias da ANP foram ?quelas compreendidas na faixa de 20-40% de biodiesel de mamona adicionado, o que as tornam candidatas ? substituta do diesel f?ssil