Oxidative desulfurization of thiophene derivatives with L-proline/benzene sulfonic acid deep eutectic solvent and their interaction: An experimental and computational study

Abstract

Oxidative desulfurization (ODS) technology is a promising technology to produce clean fuel owing to its mild operating conditions and no hydrogen requirements. However, the present works are only focused on the desulfurization of a specific sulfide, while several kinds of sulfides are existed in real fuel. For the purpose of industrial application of ODS, it is meaningful to remove several thiophene derivatives by one catalysis system. Thus, a L-proline/benzenesulfonic acid deep eutectic solvent (DES) was prepared in this work to investigate the removal of three thiophene derivatives, such as dibenzothiophene (DBT), benzothiophene (BT) and 4, 6-dimethyldibenzothiophene (4, 6-DMBDT). It was found that the removal of 4, 6-DMDBT was sensitive to temperature and O/S molar ratios whereas BT removal was affected by them to a lesser degree. At proper conditions, sulfur removal efficiencies of 100%, 99.50% and 97.15% were achieved for DBT, BT, 4, 6-DMDBT, respectively. The DES exhibited excellent stability after the addition of H2O2. The removal efficiency of DBT reached 98.16% after 10 runs. Both transition states energy barriers and interaction energy were calculated through density functional theory (DFT) computation. It was found that the interaction energy between BT and DES was −63.36 kJ/mol, which was the strongest interaction among three sulfides. This could be the key factor for the good removal efficiency of BT. The design of a catalysis system with good interaction with sulfides could lead to high ODS efficiencies based on this study.