Extraction-oxidation desulfurization by pyridinium-based task-specific ionic liquids

The Bronsted acidic ionic liquids N-carboxymethylpyridine hydrosulphate ([CH2COOHPy][HSO4]) and N-carboxyethylpyridine hydrosulphate ([(CH2)(2)COOHPy][HSO4]) were synthesized and used as the extractant and catalyst for the extraction-oxidation desulfurization of model oil. The structures of the ILs were confirmed by H-1 NMR and C-13 NMR. The density, viscosity and acid strength of the ILs were also investigated. The acid strength was in order of H2SO4 (98%) > [CH2COOHPy][HSO4] > [(CH2)(2)COOHPy][ HSO4]. The [CH2COOHPy][HSO4] showed better activity during the removal of dibenzothiophene (DBT) in n-octane by a combination of extraction and oxidation, and the sulfur removal reached 99.9% under the conditions of V-model (oil) = 20 mL, V-IL = 1.2 mL, T = 30 degrees C and H2O2/S molar ratio (O/S) = 6. In the same conditions, the removal of benzothiophene (BT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) by using [CH2COOHPy][HSO4] reached 82.5% and 89.1%, respectively. Ionic liquid [CH2COOHPy][HSO4] can be recycled 9 times without a significant decrease in the sulfur removal. (C) 2012 Elsevier Ltd. All rights reserved.