Cinética da reação de transesterificação do óleo de soja para produção de biodiesel via catálise homogênea
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Data
2020-07-27
Autores
Bortoletto, Gabriela de Carra [UNIFESP]
Orientadores
Gomes, Eliezer Ladeia [UNIFESP]
Tipo
Trabalho de conclusão de curso de graduação
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Resumo
O Brasil possui muitas espécies de vegetais que podem ser utilizadas na produção do
biodiesel. A oleaginosa mais produzida no Brasil é a soja, sendo o segundo maior
produtor mundial. Pelo fato de ser produzido a partir de fontes renováveis (óleos vegetais,
gorduras animais e óleo de microalga) e por apresentar características similares ao
diesel, o biodiesel passou a ser de grande interesse. No presente trabalho estudou-se a
cinética da reação de transesterificação do óleo de soja via catálise homogênea a fim de
se verificar a conversão de triacilglicerol em biodiesel em função do tempo para diferentes
temperaturas utilizando metanol e como catalisador o NaOH. Foram realizadas reações
em diferentes temperaturas, 35 a 60 °C, de forma a determinar-se os parâmetros
cinéticos globais desta reação e acompanhar a evolução da conversão do biodiesel a fim
de se verificar como esta variável muda com o tempo. Para a caracterização do óleo de
soja e do biodiesel utilizaram-se técnicas físico-químicas como Espectroscopia de
Ressonância Magnética Nuclear de Hidrogênio e Cromatografia Líquida de Alta Eficiência
(CLAE). A partir dos espectros de RMN 1H foi possível caracterizar o óleo de soja, o
biodiesel e os subprodutos da reação, além de se obter a conversão do óleo de soja para
cada tempo de reação. Como um dos principais resultados, tem-se a conversão final da
reação após 240 min, de 95,0% do óleo de soja em biodiesel na temperatura de 35 °C,
97,4% a 45 °C, 97,7% a 50 °C e 94,0% a 60 oC. Obteve-se resultados coerentes com a
literatura para os modelos simplificados supondo-se reações irreversíveis de pseudo-1ª
ou 2ª ordem, aplicada para a reação global. O modelo de pseudo-1ª ordem foi o mais
coerente em termos de valores e ajustes aos dados experimentais, com um bom ajuste.
Para as determinações das energias de ativação utilizando ambos os modelos, para 3
pontos utilizando somente a técnica RMN 1H, obteve-se valores de Eap= 39,78 kJ.mol-1 e
k0=4,665.105 min-1 para o modelo de pseudo-1ª ordem e para o modelo pseudo-2ª ordem
obteve-se Eap=43,40 kJ.mol-1 e k0=7,107.106min-1
. Ambas as técnicas de RMN 1H e CLAE
apresentaram resultados coerentes, porém quando combinadas não apresentaram
valores precisos.
Brazil has many species of vegetables that can be used in the production of biodiesel. The most produced oilseed in Brazil is soy, being the second largest producer in the world. Due to the fact that it is produced from renewable sources (vegetable oils, animal fats and microalgae oil) and because it has characteristics similar to diesel, biodiesel has become of great interest. In the present work, the kinetics of the transesterification reaction of soybean oil via homogeneous catalysis were studied in order to verify the conversion of triacylglycerol to biodiesel as a function of time for different temperatures using methanol and as a catalyst NaOH. Reactions were carried out at different temperatures, 35 to 60 °C, in order to determine the global kinetic parameters of this reaction and to follow the evolution of biodiesel conversion in order to verify how this variable changes with time. For the characterization of soybean oil and biodiesel, physicochemical techniques were used, such as Hydrogen Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography (HPLC). From the 1H NMR spectra it was possible to characterize soybean oil, biodiesel and reaction by-products, in addition to obtaining the conversion of soybean oil for each reaction time. As one of the main results, there is the final conversion of the reaction after 240 min, from 95.0% of soy oil to biodiesel at a temperature of 35 °C, 97.4% at 45 °C, 97.7% at 50 °C and 94.0% at 60 °C. Results were consistent with the literature for simplified models assuming irreversible reactions of pseudo-1st or 2nd order, applied to the global reaction. The pseudo-1st order model was the most coherent in terms of values and adjustments to the experimental data, with a good fit. For the determination of activation energies using both models, for 3 points using only the 1H NMR technique, values of Eap = 39.78 kJ.mol-1 and k0 = 4.665.105 min-1 were obtained for the pseudo-model. 1st order and for the pseudo-2nd order model, Eap = 43.40 kJ.mol-1 and k0 = 7.107.106 min-1 were obtained. Both 1H NMR and HPLC techniques showed coherent results, but when combined they did not present precise values.
Brazil has many species of vegetables that can be used in the production of biodiesel. The most produced oilseed in Brazil is soy, being the second largest producer in the world. Due to the fact that it is produced from renewable sources (vegetable oils, animal fats and microalgae oil) and because it has characteristics similar to diesel, biodiesel has become of great interest. In the present work, the kinetics of the transesterification reaction of soybean oil via homogeneous catalysis were studied in order to verify the conversion of triacylglycerol to biodiesel as a function of time for different temperatures using methanol and as a catalyst NaOH. Reactions were carried out at different temperatures, 35 to 60 °C, in order to determine the global kinetic parameters of this reaction and to follow the evolution of biodiesel conversion in order to verify how this variable changes with time. For the characterization of soybean oil and biodiesel, physicochemical techniques were used, such as Hydrogen Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography (HPLC). From the 1H NMR spectra it was possible to characterize soybean oil, biodiesel and reaction by-products, in addition to obtaining the conversion of soybean oil for each reaction time. As one of the main results, there is the final conversion of the reaction after 240 min, from 95.0% of soy oil to biodiesel at a temperature of 35 °C, 97.4% at 45 °C, 97.7% at 50 °C and 94.0% at 60 °C. Results were consistent with the literature for simplified models assuming irreversible reactions of pseudo-1st or 2nd order, applied to the global reaction. The pseudo-1st order model was the most coherent in terms of values and adjustments to the experimental data, with a good fit. For the determination of activation energies using both models, for 3 points using only the 1H NMR technique, values of Eap = 39.78 kJ.mol-1 and k0 = 4.665.105 min-1 were obtained for the pseudo-model. 1st order and for the pseudo-2nd order model, Eap = 43.40 kJ.mol-1 and k0 = 7.107.106 min-1 were obtained. Both 1H NMR and HPLC techniques showed coherent results, but when combined they did not present precise values.