Optimization of Base Oil Regeneration from Spent Engine Oil via Solvent Extraction

Regeneration of base oil from spent engine oil (SEO) has been studied and the parameters involved were optimized using Response Surface Methodology. A mathematical model was obtained for the dependent variables, base oil yield (Y1) and ash content (Y2) while effects of solvent to oil ratio and time were determined. From the analysis of variance, the quadratic model generated for the dependent variables, Y1 and Y2 are significant with f-values of 3764.26 and 161.84, respectively. This simply implies that the predicted values generated by the model equations are in good correlation with the experimental values for both responses, the adequacy of the model was further depicted by the ‘lack of fit’ which are not significant. Also, the coefficients of determination (R2) of 0.9996 and 0.9914 for Y1 and Y2 which are very close to unity show that the regression model explains the experimental data by 99.96% and 99.14%, respectively. Increase in solvent to oil ratio gave an increment in the base oil yield and reduced the ash content, but increase in reaction time had little or no effect on the yield and increased the ash content which is not desirable. The optimum conditions obtained are; solvent to oil ratio of 5:1 and 30 min reaction time at ambient temperature. The level of contaminants in the SEO was determined by its kinematic viscosity, viscosity index, ash content, heavy metal content, pour point and specific gravity. The method revealed an environmentally friendly way of managing engine spent oil.