Optimization of oxidative desulfurization of dibenzothiophene using acidic ionic liquid as catalytic solvent

The oxidative desulfurization of dibenzothiophene (DBT) in n-octane as model oil with Brِnsted acidic ionic liquids (ILs) N-methyl-pyrrolidonium phosphate ([Hnmp]H2PO4) as catalytic solvent and H2O2 as oxidant was optimized by orthogonal experiments. 99.8% of DBT in the model oil was removed under the optimal conditions of molar ratio of H2O2 to sulfur of 16:1, reaction temperature of 60°C, reaction time of 5 h, and volume ratio of model oil to ILs of 1:1. The desulfurization efficiency of actual diesel was 64.3% under the optimized conditions. The influences of the desulfurization efficiency of DBT decreased in the following order: oxidation temperature > oxidation time> molar ratio of H2O2/sulfur (O/S) > volume ratio of [Hnmp]H2PO4 to model oil (VIL/Vmodel oil), according to extreme analysis of orthogonal test. The IL [Hnmp]H2PO4 can be recycled six times without a significant decrease in activity.