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Biodiesel production by oleic acid methanolysis over waste biomass hydrochar catalysts
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Resumo(s)
Abordar as alterações climáticas requer uma transição dos combustíveis fósseis para fontes de
energia renováveis. O biodiesel apresenta-se como uma alternativa promissora ao gasóleo
convencional. Para aumentar a sustentabilidade do biodiesel, é crucial utilizar óleos de fritura
usados como matéria-prima. A transesterificação ácida oferece um método mais eficiente para
o processamento desses óleos em comparação com a catálise básica. Embora os
catalisadores ácidos homogéneos, como o ácido sulfúrico, sejam comumente utilizados, a sua
natureza corrosiva e os riscos de segurança associados destacam a necessidade de
substitutos. Em resposta, surgiram catalisadores ácidos heterogéneos como substitutos
viáveis. Este estudo explora a esterificação do ácido oleico com metanol, utilizando
catalisadores à base de hidrocarvão derivados de biomassa. Os hidrocarvões foram
sintetizados a partir de amido de milho, frutose, sacarose, casca de laranja e casca de banana,
através de carbonização com sulfonação simultânea a 150°C sob pressão atmosférica. O
processo de carbonização, com a duração de 5 horas, foi realizado utilizando diferentes
quantidades de ácido sulfúrico (relação de massa de biomassa entre 1:1 e 3:1) para aumentar
a área de superfície e melhorar a grafitização e estabilidade. Os catalisadores preparados,
frescos e pós-reação, foram extensivamente caracterizados utilizando difração de raios-X
(DRX), Espectroscopia de Infravermelho (ATR-FTIR), análise termogravimétrica (TGA),
Microscopia Eletrónica de Varrimento (MEV), e a composição química foi analisada através de
espectroscopia de raios-X por dispersão de energia (EDS). O desempenho dos catalisadores
foi avaliado durante a esterificação do ácido oleico. Os catalisadores de hidrocarvão
comportaram-se de forma diferente, dependendo da sua biomassa de origem, das proporções
de sulfonação e das condições de reação. O catalisador à base de amido de milho alcançou
um rendimento notável de 76,4% de MO com uma relação molar de sulfonação de 1:5. Por
outro lado, o catalisador derivado de sacarose apresentou o maior rendimento de MO, com
90,1% numa relação molar de 1:1, embora o rendimento tenha diminuído ligeiramente à medida
que a proporção de sulfonação aumentava. Curiosamente, o hidrocarvão derivado de casca de
banana mostrou um rendimento ótimo de MO de 53,1% com uma relação de sulfonação de
3:1, diminuindo com a hidrólise; para o hidrocarvão de casca de laranja, o maior rendimento foi
de 87,8%, demonstrando um comportamento distinto influenciado pela sua estrutura e pelo
processo de sulfonação, quase não alterando os resultados do hidrocarvão derivado de
sacarose. O efeito do teor de ácido oleico e de água foi avaliado, confirmando os seus efeitos
prejudiciais. Este trabalho de tese foca-se na esterificação do ácido oleico com metanol,
utilizando vários catalisadores de hidrocarvão derivados de resíduos agrícolas e alimentares.
O principal objetivo foi otimizar as condições de reação para alcançar altos rendimentos de
oleato de metilo, promovendo simultaneamente uma produção de biodiesel sustentável e
económica. O desenho experimental empregou uma relação molar de 12:1 de metanol para
ácido oleico, com uma temperatura de reação consistente de 67°C para o refluxo total de
metanol, garantindo o ambiente de reação adequado.
Addressing climate change requires a shift from fossil fuels to renewable energy sources. Biodiesel presents a promising alternative to conventional diesel fuel. To enhance the sustainability of biodiesel, it is crucial to utilize waste frying oils as a feedstock. Acid transesterification offers a more efficient method for processing these oils compared to base catalysis. Although homogeneous acid catalysts, such as sulfuric acid, are commonly used, their corrosive nature and associated safety risks highlight the need for replacements. In response, heterogeneous acid catalysts have emerged as viable replacements. This study explores the esterification of oleic acid with methanol using biomass-derived hydrochar-based catalysts. Hydrochars were synthesized from corn starch, fructose, sucrose, orange peel, and banana peel through carbonization with simultaneous sulfonation at 150°C under atmospheric pressure. The carbonization process, lasting 5 hours, was performed using different amounts of sulfuric acid (biomass mass ratio between 1:1 and 3:1) to increase surface area and improve graphitization and stability. The prepared catalysts, fresh and post-reaction were extensively characterized using X-ray diffraction (XRD), Infrared Spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and the chemical composition was analyzed using energy-dispersive X-ray spectroscopy (EDS). The catalysts performances were evaluated during the oleic acid esterification. The hydrochar catalysts behaved differently depending on their biomass feedstock, sulfonation ratios, and reaction conditions. The cornstarch-based hydrochar catalyst achieved a notable yield of 76.4% MO at a 1:5 molar sulfonation ratio. On the other hand, the catalyst from sucrose exhibited the highest MO yield of 90.1% at a 1:1 molar ratio, though the yield slightly declined as the sulfonation ratio increased. Interestingly, the banana peel-derived hydrochar shown an optimal MO yield of 53.1% at a 3:1 sulfonation ratio and decreased as hydrolysis for orange peel hydrochar, the highest yield was 87.8%, demonstrating a distinct behavior influenced by its structure and the sulfonation process, almost not changing the results of the sucrose-based hydrochar. The effect of oleic and water content was evaluated, confirming its hindering effects. This thesis work focuses on the esterification of oleic acid with methanol using various hydrochar catalysts derived from agricultural and food wastes. The primary objective was to optimize the reaction conditions to achieve high methyl oleate yields while promoting sustainable and cost-effective biodiesel production. The experimental design employed a 12:1 molar ratio of methanol to oleic acid, with a consistent reaction temperature of 67°C for methanol total reflux, ensuring the appropriate reaction environment.
Addressing climate change requires a shift from fossil fuels to renewable energy sources. Biodiesel presents a promising alternative to conventional diesel fuel. To enhance the sustainability of biodiesel, it is crucial to utilize waste frying oils as a feedstock. Acid transesterification offers a more efficient method for processing these oils compared to base catalysis. Although homogeneous acid catalysts, such as sulfuric acid, are commonly used, their corrosive nature and associated safety risks highlight the need for replacements. In response, heterogeneous acid catalysts have emerged as viable replacements. This study explores the esterification of oleic acid with methanol using biomass-derived hydrochar-based catalysts. Hydrochars were synthesized from corn starch, fructose, sucrose, orange peel, and banana peel through carbonization with simultaneous sulfonation at 150°C under atmospheric pressure. The carbonization process, lasting 5 hours, was performed using different amounts of sulfuric acid (biomass mass ratio between 1:1 and 3:1) to increase surface area and improve graphitization and stability. The prepared catalysts, fresh and post-reaction were extensively characterized using X-ray diffraction (XRD), Infrared Spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and the chemical composition was analyzed using energy-dispersive X-ray spectroscopy (EDS). The catalysts performances were evaluated during the oleic acid esterification. The hydrochar catalysts behaved differently depending on their biomass feedstock, sulfonation ratios, and reaction conditions. The cornstarch-based hydrochar catalyst achieved a notable yield of 76.4% MO at a 1:5 molar sulfonation ratio. On the other hand, the catalyst from sucrose exhibited the highest MO yield of 90.1% at a 1:1 molar ratio, though the yield slightly declined as the sulfonation ratio increased. Interestingly, the banana peel-derived hydrochar shown an optimal MO yield of 53.1% at a 3:1 sulfonation ratio and decreased as hydrolysis for orange peel hydrochar, the highest yield was 87.8%, demonstrating a distinct behavior influenced by its structure and the sulfonation process, almost not changing the results of the sucrose-based hydrochar. The effect of oleic and water content was evaluated, confirming its hindering effects. This thesis work focuses on the esterification of oleic acid with methanol using various hydrochar catalysts derived from agricultural and food wastes. The primary objective was to optimize the reaction conditions to achieve high methyl oleate yields while promoting sustainable and cost-effective biodiesel production. The experimental design employed a 12:1 molar ratio of methanol to oleic acid, with a consistent reaction temperature of 67°C for methanol total reflux, ensuring the appropriate reaction environment.
Descrição
Palavras-chave
Hidrocarvão Esterificação Oleato de metilo Biodiesel Catalisadores Hydrochar Esterification Methyl oleate Catalysts