Preparação, caracterização e avaliação de óxidos de ferro e cobalto suportados em carvão ativado polimérico como catalisador na reação de desidrogenação do etilbenzeno
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2010-02-09
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Universidade Federal de Goiás
Resumo
In this work were synthesized catalysts supported on activated carbons, which
were obtained by carbonization of a polymer matrix. The precursor of activated
carbon was the sulfonated styrene-divinylbenzene copolymer, which was
synthesized by suspension polymerization in the presence of inert diluents to
produce a macroporous network structure. The chemical modification was
performed by sulfonation with concentrated sulfuric acid in the presence of
dichloroethane. The supported catalysts were obtained by two routes. In the
first one oxides were co-precipitated on the modified copolymer, and then the
polymer was subjected to heat treatment and carbonization followed by
activation. In the second route, the copolymer was first carbonized and
subjected to activation, and then oxides were produced by co-precipitation of
metalic ions. In both cases the coprecipitation involved two steps: incorporation
of iron and cobalt ions through an ion exchange process and then coprecipitation
in alkaline and oxidizer medium. The heat treatment consists of a
heating step at 250 ° C in air atmosphere, carbonization at 900 ° C under
nitrogen atmosphere and activation at 900 º C with a flow of nitrogen saturated
with water vapor. The influence of the percentage of cobalt relative to iron in the
material properties as well as catalytic activity in the reaction of
dehydrogenation of ethylbenzene was investigated. The materials were
characterized by their magnetism, infrared spectroscopy, X-ray diffraction,
chemical analysis, Mossbauer spectroscopy, optical microscopy,
measurements of porosity by nitrogen adsorption and catalytic activity in the
reaction of catalytic dehydrogenation of ethylbenzene with water vapor. It was
observed that the materials prepared by the two different routes have properties
quite different as the amount of metal incorporated, the formation of oxides and
textural properties. It was observed that the thermal treatments influence
dramatically in the oxidation state of iron due to various reactions of oxidation
and reduction occurring during the stages of synthesis and catalytic evaluation.
The catalysts obtained by the two routes had better textural properties than the
commercial catalyst. All supported catalysts obtained were active in the reaction
of dehydrogenation of ethylbenzene. Even the support of activated carbon
oxidized with nitric acid showed catalytic activity. Among the catalysts
synthesized, those obtained by the second route had the best conjugated
results of conversion and selectivity for the reaction, especially those
synthesized with oxidized activated carbon. These catalysts are the most
promising due their textural properties and surface functional groups of
activated carbon.
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Citação
OTTO, Carlos Rangel Neves. Preparation, characterization and evaluation of iron oxides
and cobalt supported on activated carbon and polymeric
catalysts for the dehydrogenation of ethylbenzene. 2010. 117 f. Dissertação (Mestrado em Educação em Química) - Universidade Federal de Goiás, Goiânia, 2010.