Choline chloride-based deep eutectic solvents for ultrasonic-assisted oxidative desulfurization of actual heavy crude oil

Abstract

Deep eutectic solvents (DESs) are acquiring increasing interest as ionic liquid analogues because of their wide application, low-cost characteristics and environmentally friendly. In this study, choline chloride-based (ChCl) as a type of DESs were synthesized using polyethylene glycol (PEG), and applied to reduce sulfur content of actual heavy crude oil with sulfur content 37900 ppm (3.79 wt%). The synthesized DESs were characterized using Fourier-transform infrared spectroscopy (FTIR), as well as viscosity and density measurements. The DESs were evaluated for extractive ultrasound-assisted oxidative desulfurization (EUAODS), with 30 wt% H2O2 as the oxidant and formic acid as the catalyst. This study looked at the effects of oxidative desulfurization (ODS) and single ODS under ultrasonic treatment. Different systems for DESs were tested to find the desulfurization selectivity of the better reaction system; and it was found that extractive desulfurization (EDS) removed 24.57% of the sulfur, followed by extractive and ultrasonic-assisted desulfurization (EUADS) at 26.78%, then ODS at 37.28%, with ultrasonic-assisted oxidative desulfurization (EUAODS) providing the best result of 62%. According to the comparison trials, combining DESs with ultrasonic treatment improved processing. This study contributes to the body of information on the use of ultrasonic treatment in heavy crude oil desulfurization.