Dessulfurização oxidativa do dibenzotiofeno catalisada por V2O5 suportado

A necessidade de redução da emissão de poluentes, visando diminuir os sérios problemas de poluição atmosférica enfrentados atualmente, é hoje uma das principais preocupações mundiais, provocando o surgimento de leis mais rígidas, que restringem o teor de enxofre na gasolina e no diesel. Assim, o desenvolvimento de tecnologias mais eficazes na remoção de enxofre nestes combustíveis tem recebido atenção crescente. Estas tecnologias incluem a extração física com solvente, a adsorção seletiva, processos de redução/oxidação microbiológicos e a dessulfurização oxidativa (ODS). A dessulfurização oxidativa converte os compostos de enxofre em sulfonas que podem ser facilmente separadas por processos físicos. Portanto, a ODS apresenta grande potencial para tornar-se um processo complementar a processo de hidrodessulfurização tradicional na produção de combustíveis altamente dessulfurizados. Neste contexto, este trabalho visou o estudo do desempenho de catalisadores de V2O5 suportados em alumina, sílica e sílica-alumina frente à reação de ODS do dibenzotiofeno em presença do peróxido de hidrogênio, como oxidante, e da acetonitrila, como solvente polar aprótico. Os catalisadores foram preparados por impregnação ao ponto úmido e caracterizados por difração de raios-X (DRX), análise textural, redução à temperatura programada (TPR-H2), dessorção de amônia à temperatura programa (TPD-NH3) e espectroscopia Raman. O efeito de parâmetros reacionais como quantidade de solvente, relação O/S e concentração de catalisador foram investigados, utilizando a alumina como suporte, visando estabelecer as condições reacionais que levassem a maiores valores de conversão do dibenzotiofeno (DBT). Uma vez estabelecidas estas condições, foi analisado o efeito do teor de V2O5 presente no catalisador e, posteriormente, o efeito do suporte catalítico. Os resultados obtidos mostraram a 70 C razão molar H2O2/Sde 16,6, razão carga/solvente igual a 1:1 e 100 mg do catalisador 15 % V2O5/SiO2, a conversão obtida foi de 95%

Avaliação da biodegradação do dibenzotiofeno utilizando lodos ativados

During the oil refining process a huge discard volume of water occurs, which carries the contaminants from the process. A class of contaminant compounds resulting from the petrochemical industry are the Polyaromatic Hydrocarbons (PAH's). To evaluate the biodegradation of Dibenzothiophene in refinery water a synthetic wastewater was prepared to be treated using activated sludge. For this, a 2 3 Composite Design (plus 3 central points and six axial points) was carried out. The planning had as independent variables (factors) the initial concentration of DBT, pH and time of biodegradation. Biodegradation of DBT was assayed following the parameters COD, pH, temperature, SS, VSS, FVS, SVI. Concerned to the chromatographic conditions, a methodology was validated in order to verify the presence of DBT and its metabolite, 2-HBF, in the final wastewater treated by activated sludge system using a liquid - liquid extraction coupled to HPLC / UV analysis. The parameters used for validation were DL, QL, linearity, recovery and repeatability. As for optimization, the results indicated that the studied methodology can be used in monitoring the DBT degradation and 2- HBF by activated sludge, as they showed excellent linearity values, coefficients of variation, so as satisfactory recovery percentage. COD reduction efficiency tests showed an average percentage of 64.4%. The increasing trend for the results for the TSS and VSS tests showed that the activated sludge was well tailored. The best operating conditions for the reduction of COD were observed when operated with median concentrations of DBT, a higher time to biodegradation, and pH in both the acidic range as the basic one. The biodegradability of the DBT was confirmed by determining the presence of HBF-2. The highest concentrations of HBF-2 were obtained in extreme concentrations of DBT and pH, and higher biodegradation times.

Dessulfurizacao oxidativa em diesel utilizando catalisadores abase de vanádio ou manganês

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Dessulfurização oxidativa em diesel utilizando catalisadores à base de vanádio ou manganês

The oxidative desulfurization process (ODS) of a commercial diesel fuel was performed under mild conditions in the presence of catalysts based on vanadium or manganese, supported on alumina, clays (commercial, natural and pillared) and zeolites (NaX, NaY, beta, mordenite and ZSM-5). The catalysts were synthesized by wet impregnation and characterized by X-ray diffraction, textural analysis by N2 adsorption and scanning electron microscopy. The dibenzothiophene (DBT) was used as sulfur compound in catalytic evaluation. The reactions were performed using acetonitrile as solvent and the hydrogen peroxide as oxidant at 55°C. The reaction products were analized by gas chromatography (GC-FID). In the studied conditions, the process was efficient due to the DBT was converted to its corresponding sulfone. Both DBT and corresponding sulfone were extracted by the solvent. Removals and oxidations up to 100% of sulfur compound were achieved. The catalysts supported on ZSM-5 zeolite showed are more effective for oxidation reaction of sulfur compound, presenting the best results. It was observed for oxidation reaction, that vanadium catalysts were more effective and manganese catalysts showed best results for removal of sulfur compounds