Solvent extraction of oil

Claim 1

IN THE SOLVENT REFINING OF A FEED OIL CONTAINING COBOILING AROMATIC CONSTITUENTS SOLUBLE IN A LIQUID SELECTIVE SOLVENT AND HAVING TRUE BOILING POINTS IN THE RANGE OF THE SOLVENT BOILING TEMPERATURE AND BELOW, WHEREIN THE FEED OIL IS SUBJECTED TO CONTACT IN A CHARGE OIL EXTRACTION ZONE WITH THE SOLVENT TO FORM EXTRACT AND RAFFINATE PHASES WHICH ARE SEPARATELY REMOVED FROM THE EXTRACTION ZONE AND DISTILLED TO YIELD A DISTILLATE OF SOLVENT VAPOR CONTAINING SAID CO-BOILING OIL CONSTITUENTS, LEAVING LIQUID PRODUCT RESIDUES OF OIL SUBSTANTIALLY FREE OF SOLVENT, THE IMPROVEMENT WHICH COMPRISES CONDENSING SUCH DISTILLATE SETTLING SAID CONDENSATE TO FORM A SOLVENT-RICH LIQUID PHASE, CONTACTING SAID SOLVENT-RICH LIQUID PHASE IN A LIQUID-LIQUID EXTRACTION STEP WITH A RELATIVELY HIGH MOLECULAR WEIGHT, HIGH BOILING PARAFFINIC OIL HAVING AN A. S. T. M. INITIAL BOILING POINT NOT LOWER THAN 580* F. EFFECTIVE TO SELECTIVELY DISSOLVE FROM THE SAID SOLVENT-RICH PHASE CO-BOILING AROMATIC CONSTITUENTS HAVING A BOILING POINT IN THE VICINITY OF THE BOILING POINT OF SAID SOLVENT AND BELOW, THEREBY PRODUCING A SOLVENT-RICH LIQUID HAVING A REDUCED AMOUNT OF SAID CO-BOILING CONSTITUENTS DISSOLVED THEREIN WITHDRAWING THE RESULTING SOLVENT-RICH LIQUID AND RECYCLING SAID WITHDRAWN SOLVENT LIQUID TO SAID CHARGE OIL EXTRACTION ZONE.