Síntese e caracterização de óxido de cério nanoestruturado utilizando líquidos iônicos como moldes

• Ano de defesa: 2014
• Autor(a) principal: Lucchesi, Mirella [UNIFESP]
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• dARK ID: ark:/48912/0013000020n0m
• Idioma: por
• Instituição de defesa: Universidade Federal de São Paulo
• Palavras-chave em Português: Óxido de cério; Líquido iônico; Material mesoporoso
• Link de acesso: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=1933164; http://repositorio.unifesp.br/handle/11600/48776

The unique properties of the ordered mesoporous materials (MMO), such as high surface area and pore size in nanometric scale, has stimulated the investigation of new routes to their preparation. In this context, the use of ionic liquids as soft template to the synthesis of MMO has emerged as an alternative to the triblock copolymers. In this work was showed the preparation and characterization of mesoporous cerium oxide (CeO2), using ionic liquids containing imidazolium cations, with different alkyl chains, as soft template in aqueous media. The goal was to study the influence of the LI/CeO2 molar ratio and of the size of the alkyl chain on the structural, textural and morphological properties of the materials. Primarily, it was shown the preparation and characterization of six ionic liquids: tetrafluoroborate 1-butyl-3-methylimidazolium (BMIBF4), tetrafluoroborate 1-dodecyl-3-methylimidazolium (DMIBF4), tetrafluoroborate 1-hexadecyl-3-methylimidazolium (CMIBF4), bis (trifluoromethanesulfonyl)amide 1-butyl-3-methylimidazolium (BMITf2N), bis (trifluoromethanesulfonyl)amide 1-dodecyl-3-methylimidazolium (DMITf2N) and bis (trifluoromethanesulfonyl)amide 1 - hexadecyl-3-methylimidazolium (CMITf2N). In this work, only the ionic liquids containing BF4 as anionic specie was used as template in aqueous media during the preparation of mesoporous CeO2. Structural, morphological and textural properties were studied by small-angle X-ray scattering (SAXS), transmission (TEM) and scanning (SEM) electron microscopy and adsorption/desorption nitrogen isotherms at 77 K (NAI). The redox properties were investigated using temperature-programmed reduction (TPR). The obtained materials did not show ordered mesoporous with cubic and/or bidimensional structure, as it was intended. However, it was found that the materials are porous, with spherical particles and pore diameters and/or particles in nanometric scale. It was also noted that the textural and morphological properties as well as the reducibility of the obtained oxides are affected by the molar ratio of IL used in the synthesis and the size of the alkyl chain. Those materials prepared in DMIBF4 and CMIBF¬4 resulted in the smallest and the most monodisperse particles, the smallest crystallite sizes and the highest superficial areas. The CeO2 prepared in CMIBF¬4 showed the best textural, morphological and oxi-reduction properties.