Synthesis of Zirconium Oxychloride⁃Based Deep Eutectic Solvents and Their Oxidative Desulphurization Properties

A zirconium oxychloride (ZOC)?based deep eutectic solvent (DES) was successfully prepared through thermal mixing of ethylene glycol (EG) with ZOC. The structure of the DES was systematically characterized using FT?IR and 1H NMR, confirming its successful synthesis, while its viscosity was determined using a rotational viscometer. An extraction?oxidation coupled desulfurization system was constructed using hydrogen peroxide as the oxidant and the DES as both an extractant and a catalyst. The effects of DES composition, reaction temperature, oxygen?to?sulfur molar ratio, solvent?to?oil mass ratio, and different types of sulfides on the desulfurization rate were systematically investigated. The results demonstrated that under optimal conditions (zirconyl chloride to ethylene glycol molar ratio of 1∶24, reaction temperature of 50 ℃, solvent?to?oil mass ratio of 1∶5, and oxygen?to?sulfur molar ratio of 8), the system achieves a desulfurization rate of 99.8%, 94.0%, and 69.8% for dibenzothiophene (DBT), 4,6?dimethyldibenzothiophene (4,6?DMDBT), and benzothiophene (BT) in model oil, respectively. Notably, the DES maintains a desulfurization rate of 94.9% after five reuse cycles, demonstrating excellent recyclability. Through experimental data analysis, the reaction mechanism was further elucidated, revealing the synergistic mechanism of DES in both sulfide oxidation and extraction processes.