Phenylpropanoic acid-based DESs as efficient extractants and catalysts for the removal of sulfur compounds from oil

A series of Brønsted-Lewis acidic deep eutectic solvents (DESs) of C 9 H 10 O 2 ·XZnCl 2 (X from 0.5 to 3) were synthesized by simple mixing. The DESs were characterized by infrared spectroscopy, electrospray ionization mass spectrometry, and thermogravimetric analysis. The desulfurization of a model oil was investigated using C 9 H 10 O 2 ·XZnCl 2 as the extraction agent and catalyst, and H 2 O 2 as the oxidant. The effects of the molar ratio of phenylpropanoic acid to zinc chloride, reaction temperature, oxygen to sulfur (O/S) molar ratio, and volume ratio of DESs to oil on the desulfurization rate were investigated. The optimal conditions for desulfurization were determined to be a phenylpropanoic acid to zinc chloride ratio of 2:1, a reaction temperature of 50   °C, an O/S ratio of 6, a DESs to oil volume ratio of 0.25:1, and a model oil dosage of 5   mL. Under the optimal conditions, a desulfurization rate of 99.23% in 80   min was achieved. The recyclability of the DESs was also investigated, and the results showed that the desulfurization rate decreased slightly after five runs. These results demonstrate that C 9 H 10 O 2 ·0.5ZnCl 2 DESs exhibit high desulfurization activity and stability in extraction and oxidation desulfurization systems.