Patent ID: 8246815

Claim:
A method for recovering a polar hydrocarbon selective solvent substantially free of hydrocarbons and other impurities from a solvent-rich stream containing the selective solvent, measurable amounts of heavy aromatic hydrocarbons, and polymeric materials generated from reactions among thermally decomposed or oxidized solvent, heavy aromatic hydrocarbons, and additives, which method comprises the steps of: (a) introducing a feed containing polar and less polar hydrocarbons into a middle portion of an extractive distillation column (EDC) and introducing a solvent-rich stream into an upper portion of the EDC as a selective solvent feed; (b) recovering a water-containing, less polar hydrocarbon-rich stream from a top of the EDC and withdrawing a first solvent-rich stream containing solvent and polar hydrocarbons from a bottom of the EDC; (c) introducing the first solvent-rich stream into a middle portion of a solvent recovery column (SRC), recovering a polar hydrocarbon-rich stream, that is substantially free of solvent and less polar hydrocarbons, from a top of the SRC, and removing a second solvent-rich stream from a bottom of the SRC; (d) introducing a first portion of the second solvent-rich stream into the upper portion of the EDC in step (a) as the selective solvent feed; (e) cooling a second portion of the second solvent-rich stream in step (c) and introducing the cooled second portion of the solvent-rich stream into an upper portion of a solvent cleanup zone to form a solvent phase; (f) introducing a light non-aromatic hydrocarbon-rich stream into a lower portion of the solvent cleanup zone, as a heavy aromatic hydrocarbon displacement agent, to squeeze out heavy aromatic hydrocarbons and polymeric materials from the solvent phase into a hydrocarbon phase; (g) withdrawing an accumulated hydrocarbon phase containing heavy aromatic hydrocarbons and polymeric materials from an upper portion of the solvent cleanup zone, and recovering a solvent phase containing solvent and light non-aromatic hydrocarbons, which serve as heavy aromatic hydrocarbon displacement agents, and having substantially reduced levels of heavy aromatic hydrocarbons and polymeric materials, from a lower portion of the solvent cleanup zone; and (h) introducing the solvent phase from the solvent cleanup zone in step (g) into an upper portion of the EDC in step (a) as part of a selective solvent feed to recycle purified solvent into a solvent loop.