Browsing by Author "Chaves, Eduardo S."
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- Ionic Liquid Catalyzed Reaction for Biodiesel ProductionPublication . Roman, Fernanda; Queiroz, Ana; Ribeiro, António E.; Chaves, Eduardo S.; Brito, PauloBiodiesel is a promising energy source that could replace petro-diesel. The biodiesel production with the currently employed catalysts presents drawbacks, linked to cost, environmental issues, reaction time, among others. Many researches have been shifted towards finding catalysts that are environmentally benign, allow good conversions, permit the use of low cost feedstock and lead to high quality biodiesel. Ionic Liquids (IL) are a class of catalysts that have been considered for biodiesel production, due to the fact that they may surpass some of the downsides of classical catalysts. Thus, the goal of this study is to optimize the conversion of the esterification reaction of oleic acid with methanol, by estimating the optimum conditions, using the IL 1-methylimidazolium hydrogen sulfate as catalyst, and applying a Response Surface Methodology (RSM). The experiments were delineated using the Box-Behnken Design (BBD), with 4 factors in 3 levels, leading to 27 experiments. IL, oleic acid and methanol were charged to the reactor and reaction was performed with reflux, under the determined conditions. After the reaction, the mixture was kept under refrigeration until the phases were able to be separated. The oleic acid conversion was estimated by comparing the initial acidity of the oleic acid sample and the final acidity of the biodiesel phase, according to a procedure adapted from EN 14104. The p-value obtained for the regression is smaller than 0.05 and the lack of fit is estimated as 0.265, both acquired through the Analysis of Variance (ANOVA). The regression fit was determined as R2=0.986, placing the model as reasonable and statistically reliable. In general, increasing the value of the factor also increases the response. The order of importance is: C > D > C2 > A > D2 > C*D > A2 > B*C > A*C. The reaction temperature (B) did not greatly influence the response, being statistically irrelevant to this investigation. The greater value for conversion is obtained when both parameters are set to +1. Similar analysis can be made to all interactions between factors. The best result was obtained when all 4 factors were set to their maximum value, achieving a conversion of 94.8%.
- Optimization and kinetic study of biodiesel production through esterification of oleic acid applying ionic liquids as catalystsPublication . Roman, Fernanda; Ribeiro, António E.; Queiroz, Ana; Lenzi, Giane G.; Chaves, Eduardo S.; Brito, PauloIn this study, 1-methylimidazolium hydrogen sulfate, [HMIM]HSO4, ionic liquid, was successfully applied as a catalyst in the biodiesel production through the esterification reaction of oleicacid withmethanol.A response surface methodology (RSM) known as Box-Behnken Design (BBD) was applied to optimize the main experimental reaction conditions,using a set of 27 experiments.This optimization was based on the maximization of both the conversion of oleic acid and the Fatty Acid Methyl Esters (FAME) content of the obtained biodiesel samples.It was concluded that the two most relevant parameters for both the conversionand the FAME content were the molar ratio between oleic acid and methanol and the catalyst dosage.Accordingly to the model,the optimum condition for the maximum conversion was determined as being 8h, 110 ± 2°C, 15:1M ratio methanol/oleic acid and a catalyst dosage of 15wt%,resulting in a 95% conversion and for the maximum FAME content were 8h,110 ± 2°C,14:1M ratio and a catalyst dosage of 14wt%,leading to a FAME content of 90%. The kinetics of the esterification reaction was also evaluated,and the experimental results were well described using a third-order reaction model. The kinetic parameters were experimentally determined,and the value of the activation energy was 6.8kJ/mol and the pre-exponential factor was 0.0765L2.mol−2.min−1 confirming that the ionic liquid,[HMIM]HSO4,is a good alternative for replacing traditional catalysts for biodiesel production through esterification reaction.
- Produção de biodiesel através de catálise ácida aplicando líquidos iónicosPublication . Roman, Fernanda; Queiroz, Ana; Ribeiro, António E.; Chaves, Eduardo S.; Brito, PauloO biodiesel é uma fonte energética promissora, que pode substituir completamente o diesel proveniente do petróleo. O atual método de produção do biodiesel apresenta inconvenientes, relacionados com custo de produção, problemas ambientais, tempo de produção e processos de separação e purificação. A maior parte das pesquisas tem procurado catalisadores que permitam superar os problemas associados aos processos tradicionais. Os líquidos iónicos (ILs) são uma classe de catalisadores que têm sido considerados para a produção de biodiesel. Assim, o objetivo deste trabalho foi estudar a reação de produção de biodiesel aplicando o líquido iónico hidrogenossulfato de 1-metilimidazólio como catalisador. A primeira etapa da investigação foi o estudo da reação de esterificação entre o ácido oleico e o metanol, otimizando os principais parâmetros da reação (tempo, temperatura, razão molar metanol/ácido oleico e a quantidade de catalisador) através de uma Metodologia de Superfície de Resposta (RSM) conhecida por Box-Behnken Design (BBD). Esta metodologia permite variar os fatores em três níveis (-1, 0 e +1), de forma a ajustar os dados obtidos experimentalmente a uma curva que os represente, permitindo a determinação do valor ótimo para os fatores em estudo. O valor máximo para a conversão de ácido oleico (94,8%) foi obtido quando todos os fatores estavam no seu nível máximo (temperatura 110 °C, tempo de reação 8 h, razão molar metanol/ácido oleico 15:1 e uma quantidade de catalisador 15%, em relação à massa de ácido oleico). A próxima etapa será a aplicação deste mesmo catalisador à reação de transesterificação de um óleo usado com metanol.