Efficient re-refining of used motor oil via solvent extraction and vacuum distillation: Performance optimization and quality assessment

The recycling of used motor oil is essential for reducing environmental pollution and conserving valuable resources. This study explores the re-refining of used motor oil through solvent extraction, utilizing 2-Propanol and n-Butanol as solvents. The process involved sequential dehydration, vacuum distillation, and solvent extraction to remove contaminants and recover high-quality base oil. The treated oil was characterized using ASTM standards to assess key properties, including flash point, kinematic viscosity, viscosity index, density, and metal content. Results demonstrated that 2-Propanol exhibited superior performance over n-Butanol, achieving a higher yield of up to 73% at an optimized solvent-to-oil mixing ratio of 6:1. The treated oil showed significant improvements in viscosity, density, and flash point, approaching the properties of virgin oil. While solvent extraction proved effective in refining used motor oil, further studies should focus on optimizing process parameters, integrating additive restoration to enhance oil performance, and evaluating the long-term stability of the re-refined oil for industrial applications.