A recyclable ionic liquid-oxomolybdenum(vi) catalytic system for the oxidative desulfurization of model and real diesel fuel

Abstract

The oxidative desulfurization of model and real diesel has been studied using the complex [MoO₂Cl₂(4,4′-di-tert-butyl-2,2′-bipyridine)] as (pre)catalyst, aq. H₂O₂ as oxidant, and an ionic liquid as extraction solvent. Under moderate conditions (50 °C) and short reaction times (<3 h), dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene could be completely removed from the model diesel. The (pre)catalyst 1 was transformed in situ to the active catalyst [MoO(O₂)₂(di-tBu-bipy)]. By sequentially performing extractive desulfurization and ECODS steps, 76% sulfur removal was achieved for a real diesel (S_initial = 2300 ppm). For both the model and real diesels, the catalyst/IL phase could be easily recycled and reused with no loss of desulfurization efficiency.