Síntese de esferas híbridas e seu desempenho na reação de desidrogenação do etilbenzeno na presença de dióxido de carbono

Abstract

The various possibilities of application of the mesoporous materials, such as catalysis and adsorption, it have encouraged the research in the synthesis of these materials. In addition, but less frequent, synthetic routes have been searched in order to obtain a material whose structure and grain size allow its application in industrial reactors, without the preparation of pellets. With this aim, this work shows the synthesis of Hybrid mesoporous spheres (iron oxide and/or aluminum oxide). A study was conducted to determine the best conditions for the formation of the spheres; it was observed mainly the ratio between organic and inorganic material and its correlation with the chemical properties of chitosan. It was observed that a polymer with a higher degree of polymerization stabilizes a larger amount of inorganic material in the volume of solution. The results showed a good regularity in the diameter of the spheres, and that it have a high surface area with a pores diameter in the range of mesoporous. The materials of iron oxide were tested as catalysts in the reaction of ethylbenzene dehydrogenation in the presence of carbon dioxide. The catalytic tests showed that the samples of iron oxides containing aluminum are active and selective catalysts in the ethylbenzene dehydrogenation in the presence of CO2, it was observed that the addition of aluminum improves the performance of the materials. The results of XRD, TPR and catalytic performance indicate that the aluminum oxide acts as structural and textural promoter. All compositions showed high selectivity for styrene, reaching values close to 80%. It was found that the CO2 adsorption in the basic site (lattice oxygen) compete with the ethylbenzene oxidative dehydrogenation. The catalytic results suggest that the high initial ethylbenzene conversion is due to the basic sites, and the CO2 provides condition to lower basic site consumption. However, the CO2 is not able to promote the Fe2+ oxidation and regenerate the basic site (lattice oxygen) in the iron and aluminum oxide catalysts.