Rerefining of waste lube oil via solvent extraction followed by catalytic hydrotreatment

Abstract

WITH increased time of usage, lubricating oil loses its lubricationproperties and thus must be evacuated and a fresh one replaced.Recovery of waste oil is environment friendly and economic. Thewaste lube oil was treated by N-methyl-2-pyrrolidone (NMP) + 1%KOH at different conditions as temperatures from 50 to 70 0C andsolvent feed ratio from 1/1 to 7/1. The best conditions which producegood quality raffinate with high yield at 70 0C and solvent feed ratio5/1.The fresh catalyst NiMo\Al2O3 that consists of NiO = 5.2 wt.% ,MoO3 = 23 wt.%, Al2O3 balance was applied for re-refining of the bestraffinate at different reaction temperatures range from 320 to 410 0C,hydrogen pressure ranges from 30 to 50 bars and liquid hour spacevelocity (LHSV) ranges from 0.3 to 0.7 h-1. The best conditions ofhydrotreating to produce the high quality lube oil are (temperature =350 0C, pressure = 50 bar and LHSV = 0.5 h-1).The catalytic tests carried out using both spent and rejuvenatedcatalyst (using 4 % oxalic + Fe(NO3)3 at continuous modes) under theconstant temperature, hydrogen pressure and liquid hour spacevelocity (350 0C, 50 bar, 0.5 h-1) respectively, in order to compare thehydrodesulphurization (HDS) activity of fresh, rejuvenate and spentcatalyst. The result indicated that oxalic acid treatment improved theequilibrium HDS activity of the catalyst (nearly close to theequilibrium of fresh), and also improved the quality of waste lube oil.