Used Oil is derived from petroleum, coal and shale oil, due to some external reasons during the mining,
processing and using, its original physical and chemical properties have changed. This kind of oil can not
be used again. In daily industrial production mainly includes used lubricating oil, gasoline, kerosene,
diesel, hydraulic oil, grease etc. Because of its structural stability, it is difficult degradation. January 4,
1998, the used oil was included in the hazardous waste of eighth largest category. Used oil is indeed
harmful to the environment, but also has some recovery value. More and more researchers are concerned
about this field.