Oxidative desulfurization strategies using Keggin-type polyoxometalate catalysts: Biphasic versus solvent-free systems


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.




Chemistry; Engineering


Ribeiro, SO; Granadeiro, CM; Almeida, PL; Pires, J; Capel-Sanchez, MC; Campos-Martin, JM; Gago, S; de Castro, B; Balula, SS

nossos autores



This work was partly funded through the projects REQUIMTE-LAQV [FCT (Fundacao para a Ciencia e a Tecnologia) Ref. LAQV, REQUIMTE (POCI-01-0145-FEDER-007265, UID/QUI/50006/2013)] and CENIMAT, I3N (POCI-01-0145-FEDER-007688, UID/CTM/50025/2013) and UID/MULTI/00612/2013 (CQB), financed by national funds through the FCT/MEC and when appropriate co-financed by the Fundo Europeu de Desenvolvimento Regional (FEDER) under the PT2020 Partnership Agreement. The FCT and the European Union are acknowledged for the post-graduation grants SFRH/BD/95571/2013 (to SOR) and SFRH/BPD/73191/2010 (to CMG) co-funded by Ministerio da Ciencia, Tecnologia e Ensino Superior (MCTES) and the European Social Fund through the program POPH of QREN. The authors also acknowledge the Portuguese Nuclear Magnetic Resonance Network (PTNMR).

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