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Dessulfurização oxidativa catalítica de combustíveis para um ambiente mais limpo
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Neste trabalho foram desenvolvidos e caracterizados novos materiais compostos por
nanopartículas magnéticas (ferro) como suporte de óxidos de molibdénio (MoOx) para aplicação
como catalisadores na oxidação de sulfuretos. A preparação do catalisador teve início na síntese
de nanopartículas de ferro, seguida de estabilização com sílica e ancoragem de grupos amina. A
ancoragem de grupos amina permitiu a posterior ligação das nanopartículas de óxidos de
molibdénio (MoO2 e MoO3).
Os materiais obtidos foram devidamente caracterizados através de espectroscopia de
infravermelho, e difração de raios-X de pós e por microscopia eletrónica de varrimento (SEM) e
de transmissão (TEM). Após a síntese dos catalisadores, os mesmos foram testados em reações
catalíticas de oxidação de sulfuretos a sulfóxidos e/ou sulfonas. Os produtos obtidos, sulfóxidos
e/ou sulfonas poderão ser eventualmente utilizados na indústria farmacêutica e na engenharia de
plásticos e polímeros. As reações foram realizadas variando a temperatura e outras propriedades
como o oxidante, proporção de oxidante:substrato, solvente e substratos. Os ensaios catalíticos
revelaram, na sua generalidade, resultados promissores tendo sido também estudada a
recuperação dos catalisadores devido às suas propriedades magnéticas. Em quase todas as reações
catalíticas estudadas ocorreu formação de sulfona, o objetivo deste trabalho. Nos ensaios
realizados com o catalisador contendo nanopartículas de MoO2 obtiveram-se valores de
rendimento e seletividade de 100% para a sulfona para os substratos sulfureto de difenilo e o
sulfureto de metilo fenilo. Foi ainda verificado que para este catalisador a utilização de peróxido
de hidrogénio como oxidante conduziu aos resultados mais promissores.
A partir destes resultados é possível afirmar que o catalisador que apresentou os melhores
resultados é o constituído por nanopartículas de MoO2 e que o mesmo deverá ser utilizado e
estudado extensivamente como catalisador na oxidação de sulfuretos.
In this work new materials composed by magnetic nanoparticles (iron) as support of molybdenum oxides (MoOx) were developed for later application as catalysts in the oxidation of sulfides. Preparation of the catalyst began with the synthesis of iron nanoparticles, followed by stabilization with silica and anchoring of amine groups. Anchoring of amine groups allowed the subsequent connection of molybdenum nanoparticles (MoO2 and MoO3). The obtained materials were duly characterized using infrared spectroscopy and powder Xray diffraction and scanning electron microscopy (SEM) and transmission (TEM). After the catalyst’s synthesis, they were tested in catalytic oxidation reactions of sulfides to sulfoxides and/or sulfones. The obtained products, sulfoxides and/or sulfones, can eventually be used in the pharmaceutical industry and in plastics and polymer engineering. The reactions were carried out by varying the temperature and other properties such as the oxidant, oxidant:substrate ratio, solvent, and substrates. Generally, the catalytic tests revealed promising results and it was also studied the recovery of the catalysts due to their magnetic properties. In almost all reactions, sulfone formation occurred, which was one of the main objectives of this work. In the tests carried out with the catalyst containing MoO2 nanoparticles, yield and selectivity of 100% were obtained for the sulfone to the substrate diphenyl sulfide and methyl phenyl sulfide. For this catalyst it was also verified that the use of hydrogen peroxide led to the most promising results. From these results it is possible to state that the catalyst with the greatest potential is the catalyst containing MoO2 nanoparticles and that this catalyst should be used and studied extensively as a catalyst in the oxidation of sulfides.
In this work new materials composed by magnetic nanoparticles (iron) as support of molybdenum oxides (MoOx) were developed for later application as catalysts in the oxidation of sulfides. Preparation of the catalyst began with the synthesis of iron nanoparticles, followed by stabilization with silica and anchoring of amine groups. Anchoring of amine groups allowed the subsequent connection of molybdenum nanoparticles (MoO2 and MoO3). The obtained materials were duly characterized using infrared spectroscopy and powder Xray diffraction and scanning electron microscopy (SEM) and transmission (TEM). After the catalyst’s synthesis, they were tested in catalytic oxidation reactions of sulfides to sulfoxides and/or sulfones. The obtained products, sulfoxides and/or sulfones, can eventually be used in the pharmaceutical industry and in plastics and polymer engineering. The reactions were carried out by varying the temperature and other properties such as the oxidant, oxidant:substrate ratio, solvent, and substrates. Generally, the catalytic tests revealed promising results and it was also studied the recovery of the catalysts due to their magnetic properties. In almost all reactions, sulfone formation occurred, which was one of the main objectives of this work. In the tests carried out with the catalyst containing MoO2 nanoparticles, yield and selectivity of 100% were obtained for the sulfone to the substrate diphenyl sulfide and methyl phenyl sulfide. For this catalyst it was also verified that the use of hydrogen peroxide led to the most promising results. From these results it is possible to state that the catalyst with the greatest potential is the catalyst containing MoO2 nanoparticles and that this catalyst should be used and studied extensively as a catalyst in the oxidation of sulfides.
Descrição
Tese de Mestrado, Química, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Nanopartículas magnéticas Óxidos de molibdénio Catálise heterogénea Dessulfurização oxidativa Teses de mestrado - 2024