Process for separating aromatic hydrocarbons

Claim 1

A PROCESS FOR THE EXTRACTION AND RECOVERING OF AROMATIC HYDROCARBONS FROM A LIQUID HYDROCARBON MIXTURE CONTAINING AROMATIC AND NON-AROMATIC HYDROCARBONS COMPRISING (1) INTRODUCING THE MIXTURE INTO A COUNTERFLOW MULTI-STAGE EXTRACTION SYSTEM WHEREIN THE TEMPERATURE IS MAINTAINED BETWEEN 140 AND 155*C.; (2) INTRODUCING, AT ONE END OF THE EXTRACTION SYSTEM, A HIGH BOILING, AROMATIC SELECTIVE SOLVENT HAVING A NORMAL BOILING TEMPERATURE WITHIN THE RANGE OF 225*C. TO 295*C. AND WHICH SOLVENT CONTAINS DISSOLVED WATER IN THE PROPORTION OF NOT MORE THAN 2% BY WEIGHT; (3) PASSING THE SOLVENT IN COUNTERCURRENT FLOW TO THE HYDROCARBON MIXTURE TO OBTAIN A SOLVENT EXTRACT PHASE ENRICHED IN AROMATICS; (4) REMOVING THE EXTRACT PHASE FROM THE EXTRACTION SYSTEM AND INTRODUCING SAID EXTRACT PHASE AT A TEMPERATUE BETWEEN 140* AND 155*C. WITHOUT APPRECIABLE FLASH VAPORIZATION INTO A STRIPPING ZONE, WHICH IS OPERATED AT A PRESSURE OF AT LEAST 1.5 ATMOSPHERES ABSOLUTE AND AT A TOP TEMPERATURE BETWEEN 140*C. AND 155*C. AND WITH A BOTTOM TEMPERATURE OF AT LEAST 190*C. TO SEPARATE OVERHEAD A VAPOR PHASE ENRICHED IN NON-AROMATIC HYDROCARBONS; (5) CONDENSING THE VAPORS FROM SAID ZONE AND FORMING A FIRST LIQUID PHASE CONSISTING ESSENTIALLY OF HYDROCARBONS ALONG WITH A SECOND LIQUID PHASE AND RECYCLING THEM TO THE EXTRACTION SYSTEM AFTER REMOVING SUBSTANTIALLY ALL WATER PRESENT AS THE SECOND LIQUID PHASE, WITH THE CONDENSED VAPORS BEING INTRODUCED INTO THE EXTRACTION SYSTEM BETWEEN THE INTERMEDIATE POINT OF THE SYSTEM AND THE END AT WHICH THE EXTRACTION PHASE IS WITHDRAWN; (6) WITHDRAWING THE LIQUID REMAINDER OF THE EXTRACT PHASE FROM THE STRIPPING ZONE AND COOLING THE WITHDRAWN EXTRACT PHASE BEFORE REDUCTION IN PRESSURE BY AT LEAST 15* C. TO A TEMPERATURE BETWEEN 170* AND 180*C., AND (7) DISTILLING THE COOLED EXTRACT PHASE IN A DISTILLATION ZONE OPERATED AT A PRESSURE OF LESS THAN 0.5 ATMOSPHERE ABSOLUTE AND A BOTTOM TEMPERATURE OF AT LEAST 150*C. WHICH IS AT LEAST 30*C. BELOW THE BOTTOM TEMPERATURE IN THE STRIPPING ZONE WHEREBY AN AROMATIC-RICH FRACTION IS SEPARATED AS AN OVERHEAD PRODUCT.