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

摘要

The Bronsted acidic ionic liquids N-carboxymethylpyridine hydrosulphate ([CH_2COOHPy]IHSO_4]) and N-carboxyethylpyridine hydrosulphate ([(CH_2)_2COOHPy][HSO_4]) 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 ~1H NMR and ~(13)C NMR. The density, viscosity and acid strength of the ILs were also investigated. The acid strength was in order of H_2SO_4 (98%) > [CH_2COOHPy][HSO_4] > [(CH_2)_2COO-HPy][HSO_4]. The [CH_2COOHPy][HSO_4] 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℃ and H_2O_2/S molar ratio (O/S) = 6. In the same conditions, the removal of benzothiophene (BT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) by using [CH_2C00HPy][HSO_4] reached 82.5% and 89.1%, respectively. Ionic liquid [CH_2COOHPy][HSO_4] can be recycled 9 times without a significant decrease in the sulfur removal.