| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 3.1 MB | Adobe PDF |
Resumo(s)
No presente trabalho teve-se como objetivos a avaliação das potencialidades de amostras de carvão ativado de diferentes origens para sua utilização como catalisadores bi-funcionais e suportes de catalisadores monofuncionais. Os carvões ativados usados foram quatro amostras industriais fornecidos pela empresa Ingevity, denominados pelas letras A, B, C e D, e um carvão ativado preparado em laboratório a partir de cortiça, carvão S. De forma a modificar a química superficial dos materiais foi realizado um tratamento oxidativo com HNO3 a diferentes concentrações (21 e 65% (m/m)). A imobilização da platina foi realizada por diferentes métodos, nomeadamente, mistura mecânica, impregnação, permuta iónica e mecanoquímica. Numa primeira etapa estudou-se as propriedades texturais por adsorção de N2 a -196ºC e a química superficial das amostras através da determinação do pH no ponto de carga zero (pHpzc) e por espectroscopia de infravermelho com transformada de Fourier (FTIR). Foi ainda estudada a estabilidade térmica por análise termogravimétrica e a dispersão e homogeneidade das partículas de platina no suporte por microscopia eletrónica de transmissão (TEM). Os ensaios catalíticos foram realizados para a reação de hidroisomerização do n-decano às temperaturas de 320 e 350 ºC e a reação de hidrogenação do tolueno à temperatura de 150ºC. Os catalisadores não demonstraram possuir potencialidades catalíticas como catalisadores bifuncionais na reação de hidroisomerização de n-decano, uma vez que para todas as amostras estudadas a conversão catalítica não foi além de 5.7%, e uma seletividade aos produtos mais desejados (isómeros monoramificados) de 12.25%. Com o objetivo de estudar as potencialidades dos carvões ativados como suportes de partículas metálicas, os materiais forma testados na reação de hidrogenação do tolueno, de modo a caracterizar a dispersão das partículas metálicas, tendo-se obtido uma correlação linear entre a conversão catalítica e o tamanho médio de partículas metálicas imobilizadas nos carvões ativados.
Abstract The objective of this work was to evaluate the potential of activated carbon samples from different sources for their use as bifunctional catalysts and monofunctional catalyst supports. The activated carbons used were four industrial activated carbons supplied by Ingevity, called by the letters A, B, C and D, and one activated carbon prepared in the laboratory from cork, called S-carbon. To modify the surface chemistry of the materials, an oxidative treatment with HNO3 was performed at different concentrations (21 and 65% (w/w)). The deposition of platinum was performed by different methods, namely mechanical mixing, impregnation, ion exchange, and mechanochemistry. In the first stage, the textural properties by adsorption of N2 at -196ºC and the surface chemistry of the samples were studied by pH determination at the zero-load point (pHpzc) and by infrared spectroscopy with Fourier transform (FTIR). Thermal sstability by thermogravimetric analysis and dispersion and homogeneity of platinum particles in the support by transmission electron microscopy (TEM) were also studied. Catalytic tests were performed for the reaction of hydroisomerization of the n-decane at temperatures of 320 and 350ºC and for the hydrogenation reaction of toluene at a temperature of 150ºC. The catalystis did not show catalytic potential as bifunctional catalysts in the n-decane hydroisomerization reaction, since for all samples studied, catalytic conversion was not beyond 5.7%, with selectivity in the most desired products (monobranched isomers) of 12.25%. To study the potential of activated carbons as supports for metallic particles, the materials were tested in the hydrogenation reaction of toluene to characterize the dispersion of metallic particles. The results showed a linear correlation between catalytic conversion and the average size of metallic particles immobilized on activated carbons.
Abstract The objective of this work was to evaluate the potential of activated carbon samples from different sources for their use as bifunctional catalysts and monofunctional catalyst supports. The activated carbons used were four industrial activated carbons supplied by Ingevity, called by the letters A, B, C and D, and one activated carbon prepared in the laboratory from cork, called S-carbon. To modify the surface chemistry of the materials, an oxidative treatment with HNO3 was performed at different concentrations (21 and 65% (w/w)). The deposition of platinum was performed by different methods, namely mechanical mixing, impregnation, ion exchange, and mechanochemistry. In the first stage, the textural properties by adsorption of N2 at -196ºC and the surface chemistry of the samples were studied by pH determination at the zero-load point (pHpzc) and by infrared spectroscopy with Fourier transform (FTIR). Thermal sstability by thermogravimetric analysis and dispersion and homogeneity of platinum particles in the support by transmission electron microscopy (TEM) were also studied. Catalytic tests were performed for the reaction of hydroisomerization of the n-decane at temperatures of 320 and 350ºC and for the hydrogenation reaction of toluene at a temperature of 150ºC. The catalystis did not show catalytic potential as bifunctional catalysts in the n-decane hydroisomerization reaction, since for all samples studied, catalytic conversion was not beyond 5.7%, with selectivity in the most desired products (monobranched isomers) of 12.25%. To study the potential of activated carbons as supports for metallic particles, the materials were tested in the hydrogenation reaction of toluene to characterize the dispersion of metallic particles. The results showed a linear correlation between catalytic conversion and the average size of metallic particles immobilized on activated carbons.
Descrição
Palavras-chave
Carvões ativados industriais Tratamento oxidativo Catalisadores bifuncionais Catalisadores monofuncionais Hidroisomerização no n-decano Hidrogenação do tolueno Industrial activated coals Oxidative treatment Bifunctional catalysts Monofunctional catalysts Hydroisomerization of the n-decane Toluene hydrogenation