Recycling of lubricating oils used in gasoline/alcohol engines: Thermal characterization

Lubricating oils are complex mixtures of hydrocarbons obtained from petroleum by refining process and represent 2% of petroleum derivatives. The used lubricating oil is an important raw material for re-refining, because during its use it is not completely degraded, so it can be recovered from it, the base oil, which can be reused for the same purpose. Mineral-based lubricating oils were used for this work. It worked with two engines using the same type of oil; one of them was monitored during approximately 5000 km and the other one for 10,000 km. The base oil was then recovered from the lubricant using polar organic solvents (1-butanol, 2-propanol and methyl-ethyl-ketone) and then characterized by physicochemical analysis and thermal analysis (TG/DTG/DTA). From the solvents used in the extraction of the base oil, the best yields were methyl-ethyl-ketone, about 80% and 1-butanol, just above 70%. Already with 2-propanol, it was not satisfactory. The method used for the recovery of waste oils proved to be feasible and, the thermal analysis techniques evidenced the viability of this process.