PETROLEUM PROCESSING AND PETROCHEMICALS ›› 2026, Vol. 57 ›› Issue (8): 50-58.

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STUDY ON THE EXRACTION PERFORMANCE OF DIFFERENT SOVENTS ON WASTE LUBRICATING OIL

  

  • Received:2025-11-14 Revised:2026-03-19 Online:2026-08-12 Published:2026-07-23

Abstract:

During long-term use, the lubrication, anti-corrosion and other properties of waste lubricating oil deteriorate significantly, and its key indicators such as viscosity, sulfur content and flash point can no longer meet the service standards, but its base oil components still have recycling value. In this study, N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF) were used as single extractants to systematically investigate the effects of process conditions such as extraction time, extraction temperature and solvent-oil ratio on the extraction performance of waste lubricating oil. On this basis, the extraction effect and mechanism of the compound solvent were explored. The results show that the viscosity index of the reclaimed oil can be increased to 163.9 and 170.3 respectively by single NMP and DMF extraction, which can effectively remove some polar impurities. When 20% (mass fraction) of DMF is added to NMP to form a compound solvent, DMF can weaken the intermolecular forces of NMP, enhance its dipole-dipole interaction, and improve the targeted adsorption capacity and selectivity for polar impurities. Under the optimal process conditions of an extraction time of 60 min,an extraction temperature of 60 ℃ and a solvent-oil ratio of 2:1, the viscosity index of the reclaimed oil reaches 205.5, the mass fraction of sulfur decreases to 1.65 μg/g, and the flash point increases to 226 ℃. Combined with characterization methods, it is confirmed that oxidation products and degradation impurities are effectively removed, and the overall physicochemical indicators of the reclaimed oil meet the standard level of general lubricating oil base oil, providing theoretical support and practical reference for the industrial application of efficient and green refining technology of waste lubricating oil.

Key words: waste lubricating oil, solvent extraction, compound solvent, viscosity index, impurity removal