Desenvolvimento de catalisadores de óxido de ferro ou óxido de zirconio sulfatado para a redução de óxidos de nitrogênio com propano.




Nitrogen oxides are responsible for the three of the main phenomena related global pollution. The photochemical smog, the acid rain and the pollution of continental water by nitrate species, as well as the greenhouse effect, are related to nitrogen compounds. In the last decades several technologies have been proposed and used to reduce the emissions of nitrogen oxides from industries and automobiles. Among them, the selective catalytic reduction (SCR) of nitrogen oxides by hydrocarbons, in oxygen presence, has been extensively studied as a potential process in NOx emission control for diesel and lean-born engines with the advantage of removing the hydrocarbons. By considering these aspects, the activity of sulfated iron oxide-based catalysts and sulfated zirconia-based catalysts in the SCR of nitrogen oxides by propane was evaluated in this work. The effect of the sulfate source on the properties of the catalysts was also investigated. The precursors were prepared by precipitation techniques and impregnated with aqueous solutions of sulfuric acid, ammonium sulfate or copper sulfate, followed by calcination at 550C. Chemical analysis, Fourier transform infrared spectroscopy, X-ray diffraction, thermal analysis (DTA, TG), specific surface area measurements, temperature programmed reduction, acidity measurements (ammonia TPD), Mössbauer spectroscopy and X-ray photoelectron spectroscopy were used to characterize the samples. Hematite was produced in all iron oxide-based samples and different sulfate sources affected the areas of the catalysts as well as their activities. Hematite itself was almost inactive in NO reduction but the sulfated samples were active, regardless the sulfur source. The opposite was noted in the propane conversion. The most active catalysts in NO reduction were the samples prepared with ammonium sulfate and copper sulfate. The zirconia-based catalyst was made of monoclinic and tetragonal phases but the sulfated samples were only made of the tetragonal phase. The specific surface areas of these samples increased due to sulfur. The activity changed to both NO reduction and propane oxidation depending on the sulfate source. The most active catalysts were those prepared with copper sulfate. It was concluded that zirconia-based catalysts are more promising catalysts to (SCR) of nitrogen oxides by hydrocarbons.


catalisadores catalytic redução de óxidos de nitrogênio sulfated zirconia fisico-quimica zirconio sulfatado reduction of nitrogen oxides

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