Covalent immobilization of POM-based ILs on magnetic graphene oxide for efficient catalytic oxidative desulfurization of model fuel under solvent-free and moderate reaction conditions

Abstract

A series of divanado-substituted phosphomolybdic acid-based ionic liquids was successfully prepared and immobilized on the surface of a magnetic graphene oxide (APTES-mGO). The prepared catalysts were characterized and used in oxidative desulfurization (CODS) of model fuel in a solvent-free system. The sample of [C12mim]5PV2Mo10/APTES-mGO, with an alkyl length chain of C12, showed the highest DBT removal percentage, which helped to form a stable Pickering emulsion system. Moreover, the effect of operating conditions, including the reaction time and temperature, catalyst dosage, and O/S molar ratio, on the DBT removal efficiency of the catalyst were investigated employing response surface methodology (RSM). The results showed that the [C12mim]5PV2Mo10/ APTES-mGO was able to completely desulfurize the model fuel under the optimized conditions of 4 g catalyst per liter of the fuel, T = 45 °C, t = 30 min, and O/S = 4. The CODS performance of the catalyst in the presence of other refractory sulfur components (BT and 4,6-DMDBT) was also studied. The designed catalyst could be recovered 8 times without significant losing of its catalytic activity. In addition, 87.15% sulfur removal was achieved for an untreated real diesel sample by adding an extraction step after the CODS processes.