Browsing by Author "Silva, Ricardo Marques e"

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    Application of Al2O3/AlNbO4 in the oxidation of aniline to azoxybenzene.
    (2019) Batalha, Daniel Carreira; Luz, Sulusmon Cesar; Taylor, Jason Guy; Fajardo, Humberto Vieira; Noremberg, Bruno S.; Cherubin, Igor José da Silva; Silva, Ricardo Marques e; Gonçalves, Margarete Regina Freitas; Bergmann, Carlos Pérez; Valentini, Antoninho; Carreño, Neftalí Lenin Villarreal
    Al2O3/AlNbO4 powder was fabricated by a facile high-energy milling process. The precursor materials, Al2O3 and Nb2O5, are readily available and have very attractive properties. Moreover, the catalytic activity of the sample in the liquid phase oxidation of aniline (OA) in the presence of hydrogen peroxide as oxidant was evaluated. The catalyst was found to be highly efficient and selective in the oxidation of aniline to azoxybenzene under mild conditions. When mixed with 28% AlNbO4 the alumina-based catalyst achieved high conversion and selectivity and very similar to the pure Nb2O5.
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    Oxidation of terpenic alcohols with hydrogen peroxide promoted by Nb2O5 obtained by microwave-assisted hydrothermal method.
    (2020) Batalha, Daniel Carreira; Marins, Natália Hadler; Silva, Ricardo Marques e; Carreño, Neftalí Lenin Villarreal; Fajardo, Humberto Vieira; Silva, Márcio José da
    The present work describes the synthesis of niobium oxides by microwave-assisted hydrothermal method and their evaluation as a solid catalyst in oxidation reactions of terpenic alcohols with hydrogen peroxide. Effects of main parameters of synthesis were assessed and all the prepared catalysts were characterized by physical adsorption/ desorption analyses of nitrogen, infrared and Raman spectroscopies, scanning electron microscopy and powder X-rays diffraction analyses. The strength and number of acidic sites of the catalysts were determined by potentiometric titration. Morphological and structural characterization corroborate with the activity and selectivity achieved by the niobium oxides. The reusability of the catalyst was evaluated. The impacts of main reaction variables such as temperature, catalyst, and oxidant load were assessed. Niobium oxide demonstrated to be an effective catalyst, selectively converting the nerol (model molecule) to epoxide and aldehyde. Oxidation of various terpenic alcohols was investigated. Only geraniol and nerol were selectively epoxidized, suggesting a hydroxyl group assisted reaction. Although being also allylic alcohol, linalool was unreactive toward epoxidation due to the presence of a methyl group at the same carbon atom than the hydroxy group. The use of an environmentally cheap friendly oxidant (H2O2) and efficient solid catalyst (Nb2O5) are positive aspects of this process.