Study on desulfurization mechanism of ionic liquid extractant based on Gaussian quantitative calculation

In this paper, five kinds of ionic liquids (ILs) are selected as desulfurization extractants to study the desulfurization mechanism. Based on density functional theory (DFT), B3LYP functional and 6–31++G** basis set, Quantum chemistry calculations were carried out on each substance. And the interaction mechanism between the ionic liquid extractant, benzothiophene (BT), and N-octane (OC) was explored. Through quantitative calculation, the interaction energy between the three is obtained. Natural Bond Orbital theory (NBO) analysis, AIM analysis and RDG analysis are adopted to study the desulfurization mechanism from the second-order perturbation energy of chemical bond orbits, charge migration, hydrogen bonding, and other types of van der Waals forces, etc. The results show that in the interaction force between ILs and BT, electrostatic interaction is the main force, followed by hydrogen bonding, π-π interaction and other types of weak interactions such as van der Waals forces have a certain degree of desulfurization.