A comparative study of the solvent powers of phenol, furfural and NMP in improving the viscosity index of spent lubricating oil

In response to waste oil’s economic and environmental problems, there has been a growing trend to recycle and reuse waste lubricant oil. This has however been achieved using the most important used oil recycling technology, Re-refining. Although, many methods of used oil re-refining exist, solvent extraction has proven to be of better technical advantage compared to others on the basis of its environmental friendly nature as well as its economic viability. For the purpose of this research work, the solvent extraction process was employed using the solvents (Phenol, NMP and furfural) for the selective absorption of the residual aromatics as well as the contaminants present so as to improve principally the oil’s viscosity index (VI). The performances of these solvents were however accessed based on VI improvement and yield. The solvents were systematically varied alongside temperatures of 40, 60, 80 and 100oC and solvent to oil ratios of 1:1, 2:1, 3:1 and 4:1 respectively. NMP proved to be the best solvent over furfural and phenol in terms of VI improvement giving highest value of 105, whereas, furfural gave the best performance over NMP and phenol in terms of raffinate yield with highest yield obtained as 90%.