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Valorização de resíduos vegetais na produção de materiais porosos para síntese de catalisadores e membranas poliméricas catalíticas com aplicações na biorrefinaria
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O principal objetivo ao realizar este projeto consistiu em comprovar que através da biomassa é possível produzir carvões que possuam uma elevada atividade catalítica e também que esses carvões podem ser incorporados em membranas poliméricas. Como biomassa, foi utilizado conteira assim como carolo de milho que primeiramente, foram submetidos a um processo de ativação química com ácido fosfórico seguido de um processo de pirólise, obtendo-se assim carvão ativado. Após obter um pH igual ou superior a 6, foi possível caracterizar o carvão através da adsorção de N2 a -196ºC, por FTIR, por testes de enchimento (swelling) e também iniciar os ensaios catalíticos para averiguar o comportamento dos carvões produzidos como catalisadores na presença de certos álcoois e quando presentes na constituição de membranas poliméricas. A partir dos ensaios catalíticos foi possível perceber que, ao utilizar o carvão obtido através da conteira juntamente com o álcool isoamilico, foram obtidas elevadas taxas de conversão em diferentes temperaturas e o mesmo cenário se verificou quando nestes ensaios se utilizou membranas de PVA produzidas (com o carvão de conteira na sua constituição) juntamente com o mesmo álcool. No decorrer deste projeto também foram produzidas membranas de k-carragina, no entanto, nunca foi possível a sua utilização porque o seu processo de solidificação nunca foi realizado com sucesso. Os testes de inchamento mostraram que todas as membranas incham mais em contacto com a água do que com o etanol, o que indica que são mais hidrofílicas e contêm uma quantidade considerável de grupos polares, como grupos hidroxilo. A textura dos carvões obtidos foi caracterizada através de isotérmicas do tipo IV que apresentam também situações de histerese do tipo IV, ou seja, o mecanismo de preenchimento dos mesoporos é diferente do mecanismo de dessorção dos mesmos. Relativamente às suas áreas, o carvão da conteira possui uma área maior, logo é o carvão mais poroso e adequado para catálise. Para permitir uma melhor avaliação do carvão nas reações catalíticas foram utilizados modelos cinéticos (Eley-Rideal e Pseudo-Homógeneo) e os dados experimentais obtidos foram ajustados com sucesso aos modelos, especialmente no modelo Eley-Rideal, provando a funcionalidade do carvão como catalisador.
The main objective of this project was to prove that biomass can be used to produce carbons with high catalytic activity and that these carbons can be incorporated into polymer membranes. As biomass, corn cobs and corn kernels were used, which were first subjected to a chemical activation process with phosphoric acid followed by a pyrolysis process, thus obtaining activated carbon. After obtaining a pH equal to or greater than 6, it was possible to characterize the charcoal through N2 adsorption at -196ºC, by FTIR, by swelling tests, and to begin catalytic tests to investigate the behavior of the charcoals produced as catalysts in the presence of certain alcohols and when present in the composition of polymer membranes. From the catalytic tests, it was possible to see that, when using the charcoal obtained through the tailings together with isoamyl alcohol, high conversion rates were obtained at different temperatures, and the same scenario was observed when PVA membranes produced (with tailings charcoal in their composition) were used in these tests together with the same alcohol. During this project, k-carrageenan membranes were also produced; however, it was never possible to use them because their solidification process was never successfully carried out. Swelling tests showed that all membranes swell more in contact with water than with ethanol, indicating that they are more hydrophilic and contain a considerable number of polar groups, such as hydroxyl groups. The texture of the charcoals obtained was characterized by type IV isotherms, which also present type IV hysteresis situations, i.e., the mechanism of filling the mesopores is different from the mechanism of desorption of the same. Regarding their areas, the charcoal from the tailings has a larger area, so it is the most porous charcoal and suitable for catalysis. To allow for a better evaluation of the charcoal in catalytic reactions, kinetic models (Eley-Rideal and Pseudo-homogeneous) were used, and the experimental data obtained were successfully adjusted to the models, especially the Eley-Rideal model, proving the functionality of charcoal as a catalyst.
The main objective of this project was to prove that biomass can be used to produce carbons with high catalytic activity and that these carbons can be incorporated into polymer membranes. As biomass, corn cobs and corn kernels were used, which were first subjected to a chemical activation process with phosphoric acid followed by a pyrolysis process, thus obtaining activated carbon. After obtaining a pH equal to or greater than 6, it was possible to characterize the charcoal through N2 adsorption at -196ºC, by FTIR, by swelling tests, and to begin catalytic tests to investigate the behavior of the charcoals produced as catalysts in the presence of certain alcohols and when present in the composition of polymer membranes. From the catalytic tests, it was possible to see that, when using the charcoal obtained through the tailings together with isoamyl alcohol, high conversion rates were obtained at different temperatures, and the same scenario was observed when PVA membranes produced (with tailings charcoal in their composition) were used in these tests together with the same alcohol. During this project, k-carrageenan membranes were also produced; however, it was never possible to use them because their solidification process was never successfully carried out. Swelling tests showed that all membranes swell more in contact with water than with ethanol, indicating that they are more hydrophilic and contain a considerable number of polar groups, such as hydroxyl groups. The texture of the charcoals obtained was characterized by type IV isotherms, which also present type IV hysteresis situations, i.e., the mechanism of filling the mesopores is different from the mechanism of desorption of the same. Regarding their areas, the charcoal from the tailings has a larger area, so it is the most porous charcoal and suitable for catalysis. To allow for a better evaluation of the charcoal in catalytic reactions, kinetic models (Eley-Rideal and Pseudo-homogeneous) were used, and the experimental data obtained were successfully adjusted to the models, especially the Eley-Rideal model, proving the functionality of charcoal as a catalyst.
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Milho (Zea mays) Conteira (Hedychium gardnerianum) Carvão ativado Membranas poliméricas Catálise Heterogénea Corn (Zea mays) Kahili Ginger (Hedychium gardnerianum) Activated carbon Polymer membranes Heterogeneous catalysis