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Browsing by Issue Date, starting with "2019-08-01"

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  • Oxidative desulfurization strategies using Keggin-type polyoxometalate catalysts: Biphasic versus solvent-free systems
    Publication . Ribeiro, Susana; Granadeiro, Carlos; Almeida, Pedro L.; Pires, João; Capel-Sanchez, Maria C.; Campos-Martin, J. M.; Gago, S.; De Castro, Baltazar; Balula, Salete
    Strategic polyoxometalate Keggin-type structural modification was performed to increase the oxidative catalytic performance to desulfurize model and real diesels. The most active lacunar structure [PW11O39](7-) (PW11) showed to complete desulfurize a simulated diesel after 60 min at 70 degrees C. Its application as homogeneous catalyst using a biphasic system 1: 1 diesel/acetonitrile needed to use an excess of oxidant (ratio H2O2/S = 8). The immobilization of the PW11 on amine-functionalized SBA-15 supports originated two heterogeneous catalysts PW11@aptesSBA-15 and PW11@tbaSBA-15. The best results were attained with the PW11@aptesSBA-15 catalyst showing identical oxidative desulfurization performance as the homogeneous analogue. As advantage, this heterogeneous catalyst promotes the complete desulfurization of simulated diesel using a solvent-free system, i.e. without the need of acetonitrile use. On the other hand, the same desulfurization efficiency could be achieved using half the amount of oxidant (H2O2/S = 4). The oxidative desulfurization of the real diesel achieved a remarkable 83.4% of efficiency after just 2 h. The recycling capacity of PW11@aptesSBA-15 catalyst was confirmed for eight consecutive cycles using the biphasic and the solvent-free systems. Its stability investigation demonstrates to be higher under the solvent-free system than the biphasic system, without practically any occurrence of PW11 leaching in the first case. On the other hand, the Venturello peroxocomplex [PO4{W(O-2)(2)}(4)](3-), recognized as active intermediate in the homogeneous biphasic system, was not identified in the heterogeneous catalytic systems.
    2019-08-01Journal article Restricted access Show more
  • Clinical nutrition in our hand: examining clinical dietitians perception, motives of use, and engagement with nutrition apps
    Publication . Miranda, Sandra; Antunes, Ana Cristina; Machado, Ana Teresa; Mendes, Lino; Cebola, Marisa
    Nutrition mobile applications (apps) are becoming increasingly popular for a wide range of users. Their accessibility and availability has turned them into a source of information with a potentially relevant role in nutritional choices and decisions (Kao & Liebowitz, 2017). Despite a growing number of studies on attitudes, perceptions and behaviors related to nutrition apps, the literature is still scarce and provides an atomist and fragmented view on these subjects (Lieffers et al., 2018).
    2019-08-01Conference object Restricted access Show more