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Materials 2018, 11(7), 1196; https://doi.org/10.3390/ma11071196

Improving the Catalytic Performance of Keggin [PW12O40]3− for Oxidative Desulfurization: Ionic Liquids versus SBA-15 Composite

1
LAQV-REQUIMTE, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
2
Department of Chemistry, CICECO—Aveiro Institute of Materials, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal
*
Authors to whom correspondence should be addressed.
Received: 16 April 2018 / Revised: 28 June 2018 / Accepted: 2 July 2018 / Published: 12 July 2018
(This article belongs to the Special Issue Polyoxometalate and Nanohybrid Materials)
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Abstract

Different methodologies were used to increase the oxidative desulfurization efficiency of the Keggin phosphotungstate [PW12O40]3− (PW12). One possibility was to replace the acid proton by three different ionic liquid cations, forming the novel hybrid polyoxometalates: [BMIM]3PW12 (BMIM as 1-butyl-3-methylimidazolium), [BPy]3PW12 (BPy as 1-butylpyridinium) and [HDPy]3PW12 (HDPy as hexadecylpyridinium. These hybrid Keggin compounds showed high oxidative desulfurization efficiency in the presence of [BMIM]PF6 solvent, achieving complete desulfurization of multicomponent model diesel (2000 ppm of S) after only 1 h, using a low excess of oxidant (H2O2/S = 8) at 70 °C. However, their stability and activity showed some weakness in continuous reused oxidative desulfurization cycles. An improvement of stability in continuous reused cycles was reached by the immobilization of the Keggin polyanion in a strategic positively-charged functionalized-SBA-15 support. The PW12@TM–SBA-15 composite (TM is the trimethylammonium functional group) presented similar oxidative desulfurization efficiency to the homogeneous IL–PW12 compounds, having the advantage of a high recycling capability in continuous cycles, increasing its activity from the first to the consecutive cycles. Therefore, the oxidative desulfurization system catalyzed by the Keggin-type composite has high performance under sustainable operational conditions, avoids waste production during recycling and allows catalyst recovery. View Full-Text
Keywords: ionic liquids polyoxometalates; sustainable oxidative desulfurization; hydrogen peroxide; functionalized-SBA-15; benzothiophene derivatives ionic liquids polyoxometalates; sustainable oxidative desulfurization; hydrogen peroxide; functionalized-SBA-15; benzothiophene derivatives
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Ribeiro, S.O.; Duarte, B.; de Castro, B.; Granadeiro, C.M.; Balula, S.S. Improving the Catalytic Performance of Keggin [PW12O40]3− for Oxidative Desulfurization: Ionic Liquids versus SBA-15 Composite. Materials 2018, 11, 1196.

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