Papers by Author: G.V. Estrela

Abstract: Currently, one of the major technological challenges refers to issues related to the emission of gaseous pollutants, particularly those based on SO_x and NO_x. Generated mainly by the burning of fossil fuels, their reduction can be achieved by changes in the conditions of refining processes, capable of adapting the legal specifications of fuel sulphur and nitrogen, or by treatment of gases exhausted. If on the one hand the industries represent an essential portion of such gases, on the other hand the automotive vehicles contribute resolutely to complement another fraction of the emissions. The growing number of diesel-powered cars in Brazil, together with the existing environmental constraints in the country, requires greater control of the indices of gaseous mixtures mentioned above, which can be decreased through reducing agents based on technologies Reducing Agents Automotive Liquids (RAAL). By injection of an aqueous solution of urea on vehicular exhaust, it is possible for example, to catalytically reduce NO_x compounds to a mixture of N₂ and H₂O. Although this project is already in development, several challenges must be overcome, such as the catalyst deactivation by biuret (present in the solution of urea), more efficient engine design and development of fuels with lower levels of nitrogen. This work aims to study the removal of biuret by commercial adsorbents, as a way to adequate the RAAL to employment systems of diesel injection.

Abstract: The use of adsorbents in the final steps during petroleum fuels refining is still the usual practice in Brazilian refineries. The production of kerosene via the Bender process still demands that the fuel goes through a bed of clay to remove nitrogen contaminants. Thus, several studies are being developed based on adsorption over clays for the removal of nitrogen and sulfur compounds. However, the major problem is the sharp decrease in the adsorbents durability. The procedure currently employed by the refineries is the one recommended by the annex 1 from ASTM D2007 methodology. By this method, the evaluation of the adsorbent capacity is done without any pretreatment for water removal. This study aimed to establish a comparison between the results obtained by ASTM D2007 with the results obtained by a procedure developed on a bench unit which comprises a pretreating stage to remove water from the adsorbents before feeding the column. The results show that the water content strongly influences the adsorption capacity of the clays, and may even spoil high-capacity adsorbents if they are not pretreated for water removal.