Extractive distillation

Claim 1

IN AN EXTRACTIVE DISTILLATION PROCESS USING PHENOL AS THE SOLVENT INTRODUCED INTO THE UPPER SECTION AN EXRACTIVE DISTILLATION ZONE ABOVE THE FEED ENTRY, FOR THE RECOVERY OF AN AROMATIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF TOLUENE AND XYLENE FROM A HYDROCARBON FEED CONTAINING A COMPOUND WHICH NORMALLY AZEOTROPES WITH PHENOL, THEREBY CAUSING SOME OF THE PHENOL TO ESCAPE OVERHEAD WITH A RAFFINATE AND WHEREIN THERE IS PROVIDED A RECTIFICATION ZONE HAVING A NUMBER OF LIQUID CARRYING PLATES BEYOND THE EXTRACTIVE DISTILLATION ZONE TO FURTHER THE SEPARATION OF THE SOLVENT FROM THE RAFFINATE, THE IMPROVEMENT WHICH COMPRISES INTRODUCING AN ALKYL PHENOL STREAM INTO THE UPPER LEVEL OF THE RECTIFICATION ZONE AND CAUSING IT TO PASS INTO THE LIQUID OF THE TRAYS OF THE RECTIFICATION ZONE AND MAINTAINING THE ALKYL PHENOL IN LIQUID PHASE THEREON, THE AMOUNT OF ALKYL PHENOL BEING 0.03 TO 0.35 VOLUME OF ALKYL PHENOL PER VOLUME OF RAFFINATE, SUFFICIENT TO REDUCE SIGNIFICANTLY THE LOSS OF PHENOL IN THE RAFFINATE, SAID ALKYL PHENOL HAVING A BOILING POINT IN EXCESS OF ABOUT 392*F. AND HAVING AT LEAST 8 ARBON ATOMS PER MOLECULE, REMOVING OVERHEAD FROM THE RECTIFICATION ZONE A RAFFINATE WITH A SIGNIFICANTLY REDUCED PHENOL CONTENT RELATIVE TO THAT EXPERIENCED IN THE ABSENCE OF THE ALKYL PHENOL, WITHDRAWING THE LIQUID COLLECTING IN THE LOWER SECTION OF THE RECTIFICATION ZONE AND PASSING SAID LIQUID TO A DISTILLATION ZONE WHEREIN THE ALKYL PHENOL IS ISOLATED AS DISTILLATION BOTTOMS FROM THE REMAINDER OF THE WITHDRAWN LIQUID AS A DISTILLATION OVERHEAD, RETURNING THE DISTILLATION OVERHEAD TO THE EXTRACTIVE DISTILLATION ZONE AND REINTRODUCING THE ALKYL PHENOL DISTILLATION BOTTOMS INTO THE UPPER LEVEL OF THE RECTIFICATION ZONE.