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

Susana O. Ribeiro, Carlos M. Granadeiro, Pedro L. Almeida, João Pires, Maria C. Capel-Sanchez, José M. Campos-Martin, Sandra Gago, Baltazar de Castro, Salete S. Balula

Research output: Contribution to journalConference articlepeer-review

28 Citations (Scopus)

Abstract

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 [PW 11 O 39 ] 7− (PW 11 ) showed to complete desulfurize a simulated diesel after 60 min at 70 °C. Its application as homogeneous catalyst using a biphasic system 1:1 diesel/acetonitrile needed to use an excess of oxidant (ratio H 2 O 2 /S = 8). The immobilization of the PW 11 on amine-functionalized SBA-15 supports originated two heterogeneous catalysts PW 11 @aptesSBA-15 and PW 11 @tbaSBA-15. The best results were attained with the PW 11 @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 (H 2 O 2 /S = 4). The oxidative desulfurization of the real diesel achieved a remarkable 83.4% of efficiency after just 2 h. The recycling capacity of PW 11 @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 PW 11 leaching in the first case. On the other hand, the Venturello peroxocomplex [PO 4 {W(O 2 ) 2 } 4 ] 3− , recognized as active intermediate in the homogeneous biphasic system, was not identified in the heterogeneous catalytic systems.

Original languageEnglish
Pages (from-to)226-236
JournalCatalysis Today
Volume333
Issue numberSI
DOIs
Publication statusPublished - 1 Jul 2019
Event8th World Congress on Oxidation Catalysis on Oxidation Processes - Challenges and Solutions (WCOC) - Krakow, Poland
Duration: 3 Sep 20178 Sep 2017

Keywords

  • Heterogeneous catalysis
  • Hydrogen peroxide
  • Oxidative desulfurization
  • Polyoxotungstates
  • Real diesel

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