Removal of thiophene from model oil by polyethylene glycol via forming deep eutectic solvents

Abstract

Abstract The removal of organosulfurs from liquid fuel has become a hot issue due to the serious environmental pollution by sulfur oxide gases. In this study, the removal of thiophene from model oil was carried out using polyethylene glycol (PEG). It was found that deep eutectic solvents formed by PEG as hydrogen bond donor and thiophene as hydrogen bond acceptor could efficiently separate thiophene from model oil. The influencing parameters in this process were discussed, such as extraction time, temperature, mass ratio of PEG to oil, and initial sulfur concentration. The results showed that the single extraction efficiency of PEG-200 and PEG-400 could reach up to 89.0% and 97.1% in optimal conditions, respectively. The extraction efficiency as high as 95.7% and 99.9% could be achieved after three extraction cycles. The kinetic equation of the extractive desulfurization was studied by in situ infrared (IR), and the kinetic constant k 1 of PEG-400 and PEG-200 was compared (k 1(PEG-400) > k 1(PEG-200)). The desulfurization mechanism of PEG was studied by IR, 1H NMR spectra, and density functional theory (DFT). The results showed that the hydrogen bond formed between hydroxyl hydrogen in PEG and sulfur atom in thiophene accounted for the high extraction efficiency.