Extractive desulfurization using ethylene glycol and glycerol-based deep eutectic solvents: engineering aspects and intensification using ultrasound

In the present study, three deep eutectic solvents (DESs), namely TBAB:2EG, TPAB:3EG, and TPAB:2G, were synthesized by using hydrogen-bond acceptors (HBAs) (tetrabutylammonium bromide (TBAB), tetrapropylammonium bromide (TPAB)), and hydrogen-bond donors (HBDs) (ethylene glycol (EG), glycerol (G)). These DESs formed eutectic points at HBA:HBD molar ratios of 1:2, 1:3, and 1:2, respectively. The prepared DESs were analyzed by FTIR, and their structures were confirmed through H-1-NMR. The performance of the prepared DES was evaluated in terms of distribution coefficient, selectivity, performance index, and capacity of solvents for extractive desulfurization. Maximum extraction efficiencies of 81%, 77%, and 72% were obtained with TBA-B:2EG, TPAB:3EG, and TPAB:2G, respectively, with optimized parameters but without the use of ultrasound. The extractive desulfurization was intensified using ultrasound that enhanced the mass transfer between the two phases. Individual and overall mass transfer coefficients in the fuel and solvent phases with and without ultra-sound have been determined. The intensified extraction indicates the positive effect of the US on the DBT extraction by DES. The decrease in efficiency due to prolonged use of the DES was regained after regeneration. The thermodynamic parameters of the sulfur extraction process have also been calculated.

Automated summary

In this study, three deep eutectic solvents (DESs) were synthesized and their structures were analyzed. These DESs were used for extractive desulfurization and the effect of ultrasound on the extraction process was investigated. The results showed that ultrasound enhanced the extraction efficiency of the DESs.