Extractive Desulfurization of Liquid Fuel with Three-Body NMP/BEN/H2O Deep Eutectic Solvents

As a new green solvent, deep eutectic solvents (DESs) have been widely studied in the fuel desulfurization industry. This study introduces for the first time a novel three-body DES synthesized from nitromethylpyrrolidone (NMP) as a hydrogen bond acceptor (HBA) and benzoic acid (BEN) and water (H2O) as hydrogen bond donors (HBDs). It is also used for extractive desulfurization (EDS) of model oil and analogue FCC gasoline. A Fourier transform infrared ( FT-IR) spectrometer was used to detect the hydrogen bond relationships among NMP, BEN, and H2O. The changes in viscosity and density of the three-body DESs also indicated the formation of intermolecular hydrogen bonds among the components and indicated the possible binding forms between the three components of DES. Three-body DESs (NMP/BEN/H2O) have higher activity, lower viscosity, and lower volatility than water-deficient two-body DESs (NMP/BEN). By adjusting the mass ratio between the three components and comparing the experimental results of desulfurization, it is shown that the three-body DES (8NMP/2BEN/0.06H2O) containing 6 wt % water has the best desulfurization performance, and its four-stage extractive desulfurization rate for the dibenzothiophene model oil (MO-3) can reach 99.8%. The results of this study may expand the application scope of H2O and provide a new type of DES for extractive desulfurization of fuel oil and other fields.