Molecular mechanism and extraction performance evaluation of diethylene glycol-based DES for extraction desulfurization process of fuel oil

From July 1, 2020, China has fully implemented the most stringent National VI emission standards for automobiles. Thiophenes (TPs) are main form of sulfur compounds in China crude oil. More than 80% of TPs is composed of dibenzothiophene (DBT). The upgrade of emission regulations will drive technological upgrades. Deep eutectic solvent (DESs) has great potential for industrial application because of its simple preparation, low cost and high extraction rate. Based on the quantum chemistry (QC), this work proposed a screening method for DESs to extract DBT from Heptane + DBT mixtures. Through quantum chemical (QC) calculation, the probability distribution of surface charge density σ (σ-profile) was obtained, and suitable DES was selected as the extractant. Molecular dynamics (MD) simulation of the microscopic behavior of the involved DESs and mixtures was carried out, and the diffusion and aggregation behavior of sulfides in DES were studied. Through the analysis of intermolecular interaction energy, radial distribution function, spatial distribution function and self-diffusion coefficient, the formation of DESs and the extraction mechanism of DBT as well as the influence of hydrogen bond acceptors (HBA)/ hydrogen bond donors (HBD) type and molar ratio were explained. The effects of process parameters and thiophene compounds on desulfurization were studied.