Surfactant-encapsulated high-nuclear polyoxometalate complexes for catalytic oxidative desulfurization of model oil

•The catalyst is a rare example of surfactant-encapsulated POMs formed by high-nuclear poly-{HPMo6} POMs.•The removal of sulfide could reach above 98% under the optimal conditions.•The catalyst can be reused 5 times with high recycling efficiency.

Two novel surfactant-encapsulated high-nuclear polyoxometalates catalysts (DODA)20[(HPMo6O21)4(O2CCH2CO2)6]·27H2O and (DODA)10[(HPMo6O21)2(C2O4)3]·11H2O have been prepared and characterized by TG, FT-IR, 1H NMR and UV–Vis. They were used for the oxidative desulfurization of model oil containing sulfur compounds such as dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), benzothiophene (BT) with H2O2 as an oxidant under mild conditions. The removal of DBT, 4,6-DMDBT and BT could reach above 98% under the optimal conditions of n(S)/n(catalyst)/n(H2O2) = 220:1:880 at 60 °C for 2.5 h, 4.5 h and 5 h respectively, which improved to be a promising catalyst in the ODS process. The oxidative reactivity of the sulfur-containing compounds decreased according to DBT > 4,6-DMDBT > BT. We investigated the main factors affecting the process including temperature, the polymeric structures of catalysts, and O/S (H2O2/DBT) molar ratio in detail. Moreover, the catalyst can be reused 5 times with high recycling efficiency.

Graphical abstractTwo new surfactant-encapsulated high-nuclear polyoxometalate catalysts composed of the poly-{PMo6} POMs, (DODA)20[(HPMo6O21)4(O2CCH2CO2)6]·27H2O (SEP-1) and (DODA)10[(HPMo6O21)2(C2O4)3]·11H2O (SEP-2), have been synthesized, and used as catalysts for the oxidative desulfurization of model oil with H2O2 as an oxidant. The removal of sulfide could reach above 98% under the optimal conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide