Rerefining of Waste Lube Oil via Solvent Extraction Followed by Catalytic Hydrotreatment

WITH increased time of usage, lubricating oil loses its lubrication properties and thus must be evacuated and a fresh one replaced. Recovery of waste oil is environment friendly and economic. The waste lube oil was treated by N-methyl-2-pyrrolidone (NMP) + 1% KOH at different conditions as temperatures from 50 to 70 degrees C and solvent feed ratio from 1/1 to 7/1. The best conditions which produce good quality raffinate with high yield at 70 degrees C and solvent feed ratio 5/1. The fresh catalyst NiMo\Al2O3 that consists of NiO = 5.2 wt.%, MoO3 = 23 wt.%, Al2O3 balance was applied for re-refining of the best raffinate at different reaction temperatures range from 320 to 410 degrees C, hydrogen pressure ranges from 30 to 50 bars and liquid hour space velocity (LHSV) ranges from 0.3 to 0.7 h(-1). The best conditions of hydrotreating to produce the high quality lube oil are (temperature = 350 degrees C, pressure = 50 bar and LHSV = 0.5 h(-1)). The catalytic tests carried out using both spent and rejuvenated catalyst (using 4 % oxalic + Fe(NO3)(3) at continuous modes) under the constant temperature, hydrogen pressure and liquid hour space velocity (350 degrees C, 50 bar, 0.5 h(-1)) respectively, in order to compare the hydrodesulphurization (HDS) activity of fresh, rejuvenate and spent catalyst. The result indicated that oxalic acid treatment improved the equilibrium HDS activity of the catalyst (nearly close to the equilibrium of fresh), and also improved the quality of waste lube oil.