Nanocompósitos: CeO2 dopado com manganês e suportado em SBA-15
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Data
2019-11-28
Autores
Genaro, Danilo Gomes [UNIFESP]
Orientadores
Tereza, Martins da Silva [UNIFESP]
Tipo
Trabalho de conclusão de curso de graduação
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Resumo
Nanocompósitos de óxidos metálicos mistos são muito estudados por apresentarem propriedades físico-químicas diferenciadas quando comparadas aos óxidos puros em escala macroscópica. Em virtude dessas propriedades, esses materiais podem ser empregados em diversos processos catalíticos com melhor eficiência catalítica. Dessa forma, neste trabalho nanopartículas de óxido de cério dopadas com manganês foram incorporadas à uma sílica mesoporosa ordenada (SMO), a SBA-15, visando obter materiais com melhores propriedades estruturais, morfológicas e texturais, como maior área superficial, e consequentemente proporcionar melhor atividade catalítica para serem aplicadas em catálise. As incorporações das espécies inorgânicas a SBA-15 foram realizadas empregando dois métodos de preparação: pós-síntese (PS) e síntese direta (SD). Foram preparados nanocompósitos apenas com manganês (SBA-15:Mny) e materiais mistos (SBA-15:CeO2x-Mny) onde x e y correspondem aos teores molares metálicos empregados que variam em 6 e 10%. Os materiais preparados foram caracterizados empregando diversas técnicas físico-químicas e o estudo comparativo das propriedades dos materiais obtidos foi realizado para averiguar qual método apresentava melhores propriedades físico-químicas e, portanto, aplicação em catálise. Os dados de espectroscopia Raman e espectroscopia vibracional na região do infravermelho com transformada de Fourier sugerem interação maior entre as espécies constituintes dos compósitos obtidos pelo método SD. Os nanocompósitos preparados pelo método PS são menos cristalinos e apresentam valores de área superficial e volume de poros menores, indicando a presença de espécies metálicas dentro dos mesoporos. Embora a morfologia dos nanocompósitos sejam semelhantes à da sílica pura, por ambos os métodos, algumas características ímpares são obtidas ao adicionar líquido iônico no meio reacional durante a síntese dos nanocompósitos por síntese direta, uma vez que ocorre aumento do volume, diâmetro de poro e área superficial dos nanocompósitos e redução na espessura de parede e, dessa forma, fornece materiais com melhores propriedades catalíticas.
Metal oxide nanocomposites are widely studied because they have different physicochemical properties when compared to pure oxides. These materials can be applied in various catalytic processes with superior efficiency. Thus, in this work manganese doped with cerium oxide nanoparticles were incorporated into an ordered mesoporous silica (SMO), the SBA-15, aiming to obtain materials with better structural, morphological and textural properties, such as larger surface area, and consequently superior catalytic activity. Incorporations of the inorganic species into SBA-15 were performed using two preparation methods: post synthesis (PS) and direct synthesis (SD). Nanocomposites were prepared only with manganese (SBA-15: Mny) and mixed materials (SBA-15: CeO2x-Mny) where x and y correspond to the metallic molar contents from 6 to 10%. The prepared materials were characterized using various physicochemical techniques and the comparative study of the properties of the obtained materials was performed to check the ones present better properties to catalysis. Raman vibrational spectroscopies suggest a interaction between the composites obtained by the SD method. The nanocomposites prepared by the PS method are less crystalline and have smaller surface area and pore volume, indicating the presence of Ce and Mn species within the mesopores. Although the morphology of nanocomposites is similar to pure silica, by both methods, different characteristics are obtained adding ionic liquid to the reaction medium during synthesis of nanocomposites by direct synthesis, since there is an increase in volume, pore diameter and surface area of nanocomposites and reduction in wall thickness and thus provides materials with better catalytic properties.
Metal oxide nanocomposites are widely studied because they have different physicochemical properties when compared to pure oxides. These materials can be applied in various catalytic processes with superior efficiency. Thus, in this work manganese doped with cerium oxide nanoparticles were incorporated into an ordered mesoporous silica (SMO), the SBA-15, aiming to obtain materials with better structural, morphological and textural properties, such as larger surface area, and consequently superior catalytic activity. Incorporations of the inorganic species into SBA-15 were performed using two preparation methods: post synthesis (PS) and direct synthesis (SD). Nanocomposites were prepared only with manganese (SBA-15: Mny) and mixed materials (SBA-15: CeO2x-Mny) where x and y correspond to the metallic molar contents from 6 to 10%. The prepared materials were characterized using various physicochemical techniques and the comparative study of the properties of the obtained materials was performed to check the ones present better properties to catalysis. Raman vibrational spectroscopies suggest a interaction between the composites obtained by the SD method. The nanocomposites prepared by the PS method are less crystalline and have smaller surface area and pore volume, indicating the presence of Ce and Mn species within the mesopores. Although the morphology of nanocomposites is similar to pure silica, by both methods, different characteristics are obtained adding ionic liquid to the reaction medium during synthesis of nanocomposites by direct synthesis, since there is an increase in volume, pore diameter and surface area of nanocomposites and reduction in wall thickness and thus provides materials with better catalytic properties.