Imidazolium-Based Ionic Liquids for Extraction of Sulfur Compounds from Real Heavy Crude Oil

In this research, the separation process by extractive desulfurization (EDS) was adopted for use with actual heavy crude oil from the Al-Daura Oil Refinery in Baghdad-Iraq, with a sulfur content of 3.79 wt%. Two types of commercial imidazolium-based ionic liquids (ILs) (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] and 1-octyl-3-methyl imidazolium nitrate [OMIM][NO3]) were employed as efficient extractants. This study investigated the influence of various parameters on the EDS process for sulfur compounds removal, including the volume ratio of the ILs to the heavy crude oil, extraction temperature, time, and use of multistage extraction. The sulfur compounds removal efficiencies using [BMIM][BF4] and [OMIM][NO3] were 37% and 19.22%, respectively. For both ILs, the efficiency was observed in a single stage of the extractive desulfurization process. The equilibrium of extraction was reached within 15 min after three cycles. The desulfurization efficiency achieved a 54.73% reduction at a volume ratio of 1:3 ILs to heavy crude oil at 35 °C. The [BMIM][BF4] had a high extraction efficiency and good reusability for as many as three cycles, indicating that its structure had not changed.