METHOD OF PURIFYING OIL LUBE FRACTIONS Russian patent published in 1999 - IPC

FIELD: petroleum processing. SUBSTANCE: purification involves extraction with N-methylpyrrolidone, which is carried out in presence of additive: ethylene oxide/propylene block copolymers based on ethylenediamine or mixture of these block copolymers with oxyethylated alkylphenols and their sulfonic acids taken in quantity 0.003 to 0.01 wt %. Method also includes recovery of N-methylpyrrolidone from raffinate and extract solutions by rectification with final distillation of solvent in steam-stripping columns; settling separation of light oil from condensed steam- stripping vapors; drying; and return of recovered N-methylpyrrolidone into extraction stage. In preferred embodiments of method, condensed vapors are settled in presence of the same additive taken in quantity 0.002 to 0.01 wt %. EFFECT: improved quality of raffinates (viscosity index rises by 1-5 points) obtained with the same yields. 3 cl, 1 dwg, 2 tbl