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Browsing by Issue Date, starting with "2017-07-25"

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  • Microwave synthesis of SAPO-11 materials for long chain n-alkanes hydroisomerization: effect of physical parameters and chemical gel composition
    Publication . Bertolo, R.; Silva, J.M.; Ribeiro, M.F.; Martins, A.; Fernandes, A.
    The present work concerns the preparation of SAPO-11 materials using microwave (MW) heating during the crystallization process. Different experimental conditions such as crystallization temperature and time were explored, together with different Si sources. The final materials were fully characterized using chemical analysis, XRD diffraction, pyridine adsorption followed by FTIR, nitrogen sorption and NMR spectroscopy and compared with the respective conventional SAPO-11 materials, synthesized using the same initial chemical composition of the gel but under conventional electric heating. The results showed that SAPO-11 materials can be synthesized in less time (within minutes) and at lower temperature (170 °C) with MW heating than with conventional heating (respectively 24 h and 200 °C). MW heating allows nanosized SAPO-11 materials to be obtained but the nature of the Si source used has a marked influence on the textural properties and, especially, on the acidity of SAPO-11. The catalytic properties of the materials (with 0.5 wt.% Pt) were evaluated in the hydroisomerization of long chain n-alkanes using n-decane as model molecule. Optimized MW samples using colloidal AS-40 Si source showed higher yields in monobranched isomers due to a joint effect of low acidity and suitable textural properties.
    2017-07-25Journal article Restricted access Show more
  • Desulfurization process conciliating heterogeneous oxidation and liquid extraction: Organic solvent or centrifugation/water?
    Publication . Ribeiro, Susana O.; Nogueira, Lucie S.; Gago, Sandra; Almeida, Pedro L.; Corvo, Marta C.; De Castro, Baltazar; Granadeiro, Carlos; Balula, Salete
    The present work presents a strategic oxidative desulfurization system able to efficiently operate under sustainable conditions, i.e. using an eco-friendly oxidant and without the need of extractive organic solvents. The catalytic performance of Eu(PW11O39)2@aptesSBA-15 was evaluated for the oxidative desulfurization of a multicomponent model diesel using a solvent-free or biphasic systems. The results reveal its remarkable desulfurization performance achieving complete desulfurization after just 2 h of reaction. Moreover, the composite has shown a high recycling ability without loss of catalytic activity for ten consecutive ODS cycles. Interestingly, under solvent-free conditions it was possible to maintain the desulfurization efficiency of the biphasic system while being able to avoid the use of harmful organic solvents. In this case, a successful extraction of oxidized sulfur compounds was found conciliating centrifugation and water as extraction solvent. Therefore, this work reports an important step towards the development of novel eco-sustainable desulfurization systems with high industrial interest.
    2017-07-25Journal article Restricted access Show more