Process for separating c-hydrocarbon mixtures, containing paraffinic, monoolefinic and diolefinic c-hydrocarbons by distillation with n-methylpyrrolidone

Claim 1

PROCESS FOR SEPARATING C5-HYDROCARBON MIXTURES, CONTAINING PARAFFINIC, MONOOLEFINIC AND DIOLEFINIC C5-HYDROCARBON FRACTIONS, INTO HYDROCARBON FRACTIONS EACH CONSISTING SUSSTANTIALLY OF ONLY ONE OF SAID FRACTIONS, WHICH COMPRISED FEEDING THE C5-HYDROCARBON MIXTURE TO THE MIDDLE PORTION OF AN EXTRACTIVE DISTILLATION COLUMN, FEEDING N-METHYLPYRROLIDONE TO THE HEAD OF SAID COLUMN TO ACT AS A SELECTIVE SOLVENT; WITHDRAWING A LIQUID SIDE-STREAM, WHICH CONTAINS SUBSTANTIALLY ONLY THE C5-MONOOLEFINES AND N-METHYLPYRROLIDONE FROM THE LOWER PORTION OF THE UPPER HALF OF THE COLUMN; RETURNING THE N-METHYLPYRROLIDONE, AFTER FREEING IT FROM THE C5-MONOOLEFINES, TO THE EXTRACTIVE DISTILLATION COLUMN AT A POINT BELOW THE WITHDRAWAL POINT; MAINTAINING THE N-METHYLPYRROLIDONE/HYDROCARBON RATIO APPROXIMATELY CONSTANT IN THE EXTRACTIVE DISTILLATION COLUMN BY EFFECTING A PARTIAL CONDENSATION OF VAPOROUS HYDROCARBONS ABOVE THE FEEDBACK POINT; WITHDRAWING THE C5-DIOLEFINES IN VAPOR FORM FROM THE LOWER PORTION OF THE EXTRACTIVE DISTILLATION COLUMN ABOVE THE SUMP; WITHDRAWING THE PARAFFINES AT THE HEAD OF THE EXTRACTIVE DISTILLATION COLUMN; AND RETURNING THE N-METHYLPYRROLIDONE COLLECTED IN THE BOTTOM OF THE EXTRACTIVE DISTILLATION COLUMN TO THE HEAD OF SAID COLUMN.