Márcia de Souza Ramos

Universidade Federal da Bahia, Bahia, Estado de Bahía, Brazil

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Publications (3)0 Total impact

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    ABSTRACT: The influence of the preparation method on the properties of catalysts based on iron and aluminum oxides for the dehydrogenation of ethylbenzene in the presence of steam to produce styrene, a product of high commercial value was studied. Samples were prepared by hydrolysis of iron nitrate and/or aluminum hydroxide with potassium by adding: (1) iron nitrate solution and the precipitating on the water, followed by impregnating the iron gel with aluminum nitrate; (2) solution of iron nitrate and aluminum and the precipitating on water and (3) solution of iron nitrate and aluminum nitrate (mixed) and the precipitating on water. It was found that the specific surface area and reducibility of the solids varied with the method of preparation. The most promising catalyst was obtained by Method 1, which led to higher styrene yield and low selectivity to benzene and toluene Se estudió la influencia del método de preparación sobre las propiedades de catalizadores basados en óxidos de hierro y aluminio para la deshidrogenación de etilbenceno en presencia de vapor de agua para producir estireno, un producto de alto valor comercial. Las muestras fueron preparadas por la hidrólisis de nitrato de hierro y/o de aluminio con hidróxido potasio por la adición de: (1) solución de nitrato de hierro y del precipitante sobre el agua, seguido por la impregnación del gel con nitrato de aluminio, (2) solución de nitrato de hierro, aluminio y el precipitante sobre el agua y (3) solución de nitrato de hierro y aluminio (mesclados) y del precipitante sobre el agua. Se observó que el área superficial específica y la reducción de los sólidos varían con el método de preparación. El catalizador más promisorio fue el obtenido por el método 1, llevó a rendimientos más altos de estireno y baja selectividad para el benceno y el tolueno.
    VII Simposio Colombiano de Catálisis; 01/2011
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    ABSTRACT: The effect of preparation method on the catalytic properties of iron oxides containing aluminum and potassium was studied in this work, in order to get efficient solids for ethylbenzene dehydrogenation in the presence of steam, the main route for the production of styrene, a high value monomer used in the manufacture of polymers and resins. Samples were prepared by hydrolysis of ferric nitrate with potassium hydroxide by different methods through the addition of: (i) the solution of salt and of the precipitant on the water, (ii) the solution of the salt on the precipitant solution and (iii) the precipitant solution on the salt solution. Also, samples were prepared by impregnating iron oxides with aluminum, using the Fe/Al = 10 molar ratio. For all cases, hematite was produced and no phase containing potassium or aluminum was detected. The reducibility of the solids was dependent on the preparation method and on aluminum. Among the methods studied, the one in which the solution of the salt was added to the precipitant solution, followed by impregnation with aluminum nitrate produced the most active and selective to styrene catalysts. Foi estudado o efeito do método de preparação nas propriedades catalíticas de óxidos de ferro contendo alumínio e potássio, com o objetivo de obter catalisadores eficientes para a desidrogenação do etilbenzeno em presença de vapor d´água, principal rota para a produção de estireno, um monômero de alto valor comercial utilizado na manufatura de polímeros e resinas. As amostras foram preparadas por hidrólise de nitrato férrico com hidróxido de potássio por diferentes métodos adicionando-se: (i) a solução do sal e da base sobre a água; (ii) a solução do sal sobre a solução da base e (iii) a solução da base sobre a solução do sal. Também foram obtidas amostras impregnando alumínio a estes sólidos, com razão molar Fe/Al=10. Em todos os casos, foi produzida hematita e não foi detectada nenhuma fase contendo potássio ou alumínio. A redutibilidade dos sólidos foi dependente do método de preparação e da presença do alumínio. Dentre os métodos estudados, aquele em que a solução do sal foi adicionada sobre a solução do agente precipitante, seguida da impregnação com nitrato de alumínio produziu os catalisadores mais ativos e seletivos a estireno.
    16CBCat - Congresso Brasileiro de Catalise; 01/2011
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    ABSTRACT: The effect of neodymium, lanthanum, aluminum and zirconium on the textural and catalytic properties of hematite was studied in this work, which aimed to develop catalysts to ethylbenzene dehydrogenation, in the presence of steam, the main commercial route to obtain styrene. Hematite and magnetite were found in fresh and spent catalysts, respectively. All dopants increased the specific surface area of the fresh and spent catalysts and made them more resistant against reduction, but only aluminum avoided sintering during reaction. The dopants increased the catalytic activity per area of hematite, except aluminum which acted only as a textural promoter. The selectivity was decreased due to zirconium and lanthanum while the other dopants did not change this parameter. The neodymium-containing catalyst showed high levels of activity and selectivity and was able to work up to 530°C, without deactivation, being the most promising with regard to styrene production.
    Applied Catalysis A-general - APPL CATAL A-GEN. 01/2008; 341(1):12-17.