Optimization of Oxidative Desulfurization of Dibenzothiophene Using a Coordinated Ionic Liquid as Catalytic Solvent

Abstract

Oxidative desulfurization (ODS) of dibenzothiophene (DBT) in n-octane with hydrogen peroxide/acetic acid using a quaternary ammonium coordinated ionic liquid (IL) (C4H9)4NBr · 2C6H11NO as catalytic solvent has been studied. The ODS mechanism by coordinated ionic liquid [(C4H9)4NBr · 2C6H11NO] was also carried out. The sulfur-containing compounds in model oil were extracted into ionic liquid phase and oxidized to their corresponding sulfones by H2O2. The effect factors for desulfurization of model oil were investigated in detail by means of monofactorial and orthogonal experiments (L16(4)4). The results showed that the desulfurization efficiency of model oil could reach 98.6% under the optimal conditions of oxidation time, oxidation temperature, molar ratio of H2O2/sulfur (O/S), and volume ratio of model oil to coordinated ionic liquid were 30 min, 50°C, 16, and 1, respectively. The influences to the desulfurization efficiency of DBT decreased in the following order: volume ratio of model oil to coordinated ionic liquid (C4H9)4NBr · 2C6H11NO (Vmodel oil/VIL) > molar ratio of O/S > oxidation temperature > oxidation time, according to extreme analysis of the orthogonal test. The coordinated ionic liquid (C4H9)4NBr · 2C6H11NO can be recycled 5 times without a significant decrease in desulfurization.