Óxidos metálicos derivados de hidrotalcitas contendo Ga3+ como catalisadores para produção de biodiesel etílico
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Data
2016-11-18
Autores
Mancini, Marcelo [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O biodiesel é um biocombustível composto por mistura de ésteres alquílicos produzidos a partir de álcoois de cadeias curtas (metanol e etanol) com glicerídeos graxos de origem vegetal ou animal e reconhecidamente causa menos impactos ambientais que o diesel fóssil. A catálise heterogênea utilizada na síntese de biodiesel apresenta muitas vantagens, como a reutilização do catalisador e menor consumo de água. A síntese de argilas aniônicas tipo hidrotalcita (Mg6Al2(CO3)(OH)16.4H2O), em diferentes razões molares dos metais M2+/M3+ (3:1;4:1;5:1) e a substituição por Ga3+ nas porcentagens de 50 e 100% pelo método de coprecipitação convencional, em banho de ultrassom, em pH ácido e com biomoldes (sacarose, amido e levedura) foi a base do trabalho desenvolvido, objetivando alterar suas propriedades catalíticas para obter catalisadores heterogêneos com altas taxas de conversão em biodiesel etílico pela reação de transesterificação de óleo de soja e etanol. A reação ocorreu por 12h a 120 oC na razão molar óleo/etanol 1:20 e 20% (m/m) de catalisador em relação ao óleo. As caracterizações dos hidróxidos duplos lamelares ocorreram por TGA-DTG, DRX, FTIR-ATR e SEM e a de seus óxidos correspondentes por B.E.T., basicidade, acidez e SEM, a atividade catalítica foi quantificada por CG-FID, obtendo conversões superiores a 70% após aumento na razão molar e inserção de gálio e até 90% utilizando amido como biomolde. No entanto, esta substituição apresentou resultados inferiores nas análises de basicidade e B.E.T. dos óxidos, mantendo as características típicas das hidrotalcitas nas análises de DRX, FTIR, TGA e SEM. Os materiais coprecipitados em banho de ultrassom e em pH ácido mantiveram algumas das características do material “tipo hidrotalcitas” e contribuíram com melhoras em determinados parâmetros, mas em um contexto geral não agregou benefícios a conversão de biodiesel etílico, reforçando que a síntese do material por coprecipitação convencional ainda é o método mais eficaz para obtenção de óxidos mistos porosos oriundos de hidróxidos duplos lamelares destinados a produção de biodiesel.
Biodiesel is a biofuel, composed of a mixture of alkyl esters produced from short-chain alcohols (methanol and ethanol) with oily glycerides of vegetable or animal origin that causes less environmental impact than fossil diesel knowingly does. Heterogeneous catalysis for biodiesel synthesis presents many advantages, such as the catalyst reutilization and less water consumption. The synthesis of anionic clay of hydrotalcite type (Mg6Al2(CO3)(OH)16.4H2O), in different molar rates of the metals M2+ /M3+ (3:1;4:1;5:1) and the substitution by Ga3+ in the percentages of 50% and 100% through the conventional coprecipitation method, in ultrasonic bath, acid pH and tamplates (sucrose, starch and yeast), is the basis of the developed work, which intended to alter the catalytic properties in order to obtain heterogeneous catalysts with high rates of conversion to ethylic biodiesel through the reaction of transesterification with soy oil and ethanol. The reaction occurred for 12 hours at 120 oC on molar rate oil/ethanol 1:20 and 20% (m/m) of catalyst in relation to the oil. The characterizations of the layered double hydroxides occurred by TGA-DTG, DRX, FTIR-ATR, and SEM, and the characterization of the corresponding oxides by B. E. T., basicity, acidity, and SEM; the catalytic activity was quantified by CG-FID, obtaining conversions superior to 70% after increase of the molar rate and insertion of gallium and up to 90% using starch as tamplate. However, this substitution presented inferior results in the analyses of basicity of DRX, FTIR, TGA, and SEM. The materials coprecipitated in ultrasonic bath and in acid pH maintained some characteristics of the hydrotalcite-like material, and contributed with improvements to some of the parameters, but in general didn’t aggregate benefits to the conversion of ethylic biodiesel. We should highlight that material synthesis by conventional coprecipitation is still the most effective method for obtaining mixed porous oxides (PMOs) from layered double hydroxides destined to biodiesel production.
Biodiesel is a biofuel, composed of a mixture of alkyl esters produced from short-chain alcohols (methanol and ethanol) with oily glycerides of vegetable or animal origin that causes less environmental impact than fossil diesel knowingly does. Heterogeneous catalysis for biodiesel synthesis presents many advantages, such as the catalyst reutilization and less water consumption. The synthesis of anionic clay of hydrotalcite type (Mg6Al2(CO3)(OH)16.4H2O), in different molar rates of the metals M2+ /M3+ (3:1;4:1;5:1) and the substitution by Ga3+ in the percentages of 50% and 100% through the conventional coprecipitation method, in ultrasonic bath, acid pH and tamplates (sucrose, starch and yeast), is the basis of the developed work, which intended to alter the catalytic properties in order to obtain heterogeneous catalysts with high rates of conversion to ethylic biodiesel through the reaction of transesterification with soy oil and ethanol. The reaction occurred for 12 hours at 120 oC on molar rate oil/ethanol 1:20 and 20% (m/m) of catalyst in relation to the oil. The characterizations of the layered double hydroxides occurred by TGA-DTG, DRX, FTIR-ATR, and SEM, and the characterization of the corresponding oxides by B. E. T., basicity, acidity, and SEM; the catalytic activity was quantified by CG-FID, obtaining conversions superior to 70% after increase of the molar rate and insertion of gallium and up to 90% using starch as tamplate. However, this substitution presented inferior results in the analyses of basicity of DRX, FTIR, TGA, and SEM. The materials coprecipitated in ultrasonic bath and in acid pH maintained some characteristics of the hydrotalcite-like material, and contributed with improvements to some of the parameters, but in general didn’t aggregate benefits to the conversion of ethylic biodiesel. We should highlight that material synthesis by conventional coprecipitation is still the most effective method for obtaining mixed porous oxides (PMOs) from layered double hydroxides destined to biodiesel production.
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Biodiesel etílico, Catálise heterogênea, Hidrotalcita, Gálio, Ethylic biodiesel, Heterogeneous catalysis, Hydrotalcite, Gallium