Effect of Extraction and Adsorption on Re-refining of Used Lubricating Oil

Solvent extraction followed by adsorption has been found to be one of the competitive processes for recycling of waste lubricating oil. In this paper, the performance of various solvents for sludge formation has been studied. 1-butanol produced maximum sludge followed by methyl ethyl ketone (MEK), 1-hexanol and 2-butanol. The difference in sludge formation between 1-butanol and MEK was only 0.3%. However due to low boiling point and low cost, MEK was preferred over 1-butanol. The extracted oil was then passed through a column of different adsorbents. An oil of colour index (yellow) 2, carbon residue 0.14%, sulphated ash 0.02% and flash point 216°C, was obtained with 94% yield.