The oxidation⁃extraction process was used to desulfurize of the visbreaking diesel oil, O3 was used as oxidant, formic acid was used as catalyst, and polar oxides such as sulfoxide and sulfone were extracted and separated from diesel oil by polar organic solvent. The effects of oxidation time, oxidation temperature, ratio of extractant to oil and amount of formic acid on the desulfurization rate of diesel oil in the reaction system were investigated, and the optimum reaction conditions were determined. The results showed that the sulfur content of visbreaking diesel oil decreased from 4 980 μg/g to 490 μg/g and the desulfurization rate was 90%. By comparing the properties of visbreaking diesel oil before and after oxidation, it can be concluded that the oxidation⁃extraction method can also improve the chromaticity and acidity of visbreaking diesel oil.

Copper tungstate was prepared by direct precipitation method at room temperature. The sample was treated with high temperature calcination and activation with hydrogen peroxide in order to improve the oxidative desulfurization activity. Then the oxidative desulfurization of dibenzothiophene (DBT) from model oil was carried out using the activated CuWO4 as catalyst, hydrogen peroxide as the oxidant, and imidazolium fluoroborate ionic liquid as extracting agent．The reaction conditions，including temperature, amount of catalyst and oxidant, types of extractant and sulfides were also studied．The results indicate the optimized desulfurization conditions of 0.4 mL of hydrogen peroxide, 0.02 g of catalyst, imidazole tetrafluoroborate as the extractant at 70 ℃ for 60 min, and the desulfurization rate can reach 93%. In addition, the desulfurization rate remains above 82% when the catalyst was reused for five times.

The pretreatment of spent lubricating oil to remove part of the water and impurities was carried out firstly, then the flash device are used for further removal of water, followed by the distillation in atmospheric and vacuum distillation unit. A lowfreezingpoint, high stable light diesel were produced in the atmospheric distillation zone; different kinds of lubricating base oils which are all available resources were produced by vacuum distillation segment combined with complex agent refiningalkaline cleaningclay refining process. Additives were added finally to improve the oil quality. The additional purification process conditions were identified: the mass fraction of acid solvent 4.5% which contains the mass fraction complexing agent 1.5% for pickling; 1% NaOH aqueous solution with its mass fraction of 40% were added for alkaline cleaning at 40 ℃, then 3% clay was added and stirred for 25～30 min at the temperature less than 120 ℃. This processing technology not only reduces the pollution effectively, but also greatly improves the reutilization of waste oil.