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Abstract(s)
A produção de biodiesel é geralmente realizada por transesterificação alcalina de óleos com baixo teor de ácidos gordos livres (AGL). Visando diminuir os custos de produção do biodiesel, óleos de baixa qualidade ou residuais têm sido investigados como alternativas de fontes de matéria-prima. No entanto, a reação catalisada com hidróxido de sódio pode apresentar problemas na etapa de purificação, causados pela formação de sabões. Neste estudo, o catalisador hidróxido de colina foi sintetizado e o seu espetro de FTIR foi comparado com o do hidróxido de colina comercial. Usando o software do próprio equipamento foi possível obter uma correspondência de 85% entre ambos. Todavia, decidiu-se utilizar o hidróxido de colina comercial para ser aplicado na produção de biodiesel, a partir de óleo de girassol virgem e residual, devido ao longo período de tempo (aproximadamente 1 semana) necessário para sintetizar o catalisador, assim como ao baixo rendimento de síntese (médio de 60%). Apresenta-se uma otimização dos principais parâmetros que influenciam a conversão dos triglicéridos e ácidos gordos livres (AGL) em ésteres metílicos de ácidos gordos (FAMEs), nomeadamente a percentagem de catalisador, o tempo e a razão molar óleo/álcool, mantendo a temperatura em 65 °C. Os valores ótimos de conversão, determinados quer através da redução do índice de acidez, quer pela percentagem mássica em FAMEs produzidos, são obtidos utilizando 4% de catalisador, uma razão óleo/metanol de 1:8, um tempo de reação de 1 h, para a referida temperatura de 65 ºC. Os produtos da reação (biodiesel), foram quantificados através de cromatografia gasosa usando o GC-FID, de modo a avaliar a produção de FAMEs. Os índices de acidez dos produtos da reação com óleo de girassol residual apresentaram uma redução significativa em relação à matéria-prima (de acidez 6,14 mgKOH/g), enquanto nas reações com óleo de girassol virgem, com índice de acidez próximo de 0,20 mg KOH/g, o índice de acidez da fase orgânica manteve-se baixo. Efetuaram-se também estudos de recuperação do hidróxido de colina que se provaram não ser eficientes nas condições testadas, pois pela análise feita por FTIR foi possível a identificação de hidróxido de colina em ambas as fases de separação. Os testes foram realizados com n-butanol/água e acetato de etilo/água e, de ambos os sistemas, o que apresentou melhores resultados foi o sistema com n-butanol.
The biodiesel production is usually performed using alkaline transesterification of oils containing low levels of free fatty acids. Aiming to shorten the biodiesel production costs, low quality oils and residual oils have been investigated as potential alternative raw material sources. However, problems in the purification phase, caused by the generation of soaps, are found in the catalysis with sodium hydroxide. In this work, the catalyst (choline hydroxide) was synthesized and compared to a commercial catalyst solution, resulting on a correlation of approximately 85%. Nevertheless, the commercial choline hydroxide was selected to be applied in the biodiesel production from residual and virgin sunflower oil. A parametric analysis was made to study the influence of the operational parameters: catalyst percentage, reaction time, and molar ratio oil/alcohol. The best conversion values were obtained under the following conditions: 4% of catalyst, molar ratio oil/methanol of 1:8, and 1 hour of reaction, for a temperature settled at 65 °C for all the reactions. The quantification of the biodiesel (through obtained the FAMEs) was carried out by gas chromatography. At these conditions, the acidity levels of the products obtained from the residual sunflower oil transesterification significantly decreased, independently on the conversion to FAMEs, no significant change was observed for the biodiesel obtained from the virgin sunflower oil, since its acidity level was initially low. Studies on the recovery of the choline chloride were also conducted, but the results were not very promising, since the FTIR analysis showed traces of choline hydroxide in both separation phases. The tests were made using n-butanol/water and ethyl/water acetate systems and, in both, choline hydroxide appeared in both phases. The tests with n-butanol presented better results, since the correlation made by FTIR was lower in the phase that should have had less glycerol.
The biodiesel production is usually performed using alkaline transesterification of oils containing low levels of free fatty acids. Aiming to shorten the biodiesel production costs, low quality oils and residual oils have been investigated as potential alternative raw material sources. However, problems in the purification phase, caused by the generation of soaps, are found in the catalysis with sodium hydroxide. In this work, the catalyst (choline hydroxide) was synthesized and compared to a commercial catalyst solution, resulting on a correlation of approximately 85%. Nevertheless, the commercial choline hydroxide was selected to be applied in the biodiesel production from residual and virgin sunflower oil. A parametric analysis was made to study the influence of the operational parameters: catalyst percentage, reaction time, and molar ratio oil/alcohol. The best conversion values were obtained under the following conditions: 4% of catalyst, molar ratio oil/methanol of 1:8, and 1 hour of reaction, for a temperature settled at 65 °C for all the reactions. The quantification of the biodiesel (through obtained the FAMEs) was carried out by gas chromatography. At these conditions, the acidity levels of the products obtained from the residual sunflower oil transesterification significantly decreased, independently on the conversion to FAMEs, no significant change was observed for the biodiesel obtained from the virgin sunflower oil, since its acidity level was initially low. Studies on the recovery of the choline chloride were also conducted, but the results were not very promising, since the FTIR analysis showed traces of choline hydroxide in both separation phases. The tests were made using n-butanol/water and ethyl/water acetate systems and, in both, choline hydroxide appeared in both phases. The tests with n-butanol presented better results, since the correlation made by FTIR was lower in the phase that should have had less glycerol.
Description
Mestrado de dupla diplomação com a UNIFACS - Universidade Salvador
Keywords
Síntese do hidróxido de colina Produção de biodiesel Transesterificação Catálise Otimização de parâmetros