Basf Aktiengesellschaft

Detlef Bender

Hans-Martin Weitz

Klaus Volkamer

Ulrich Wagner

Dieter Stockburger

Klaus-Juergen Schneider

Harald Schwentker

A process for separating, by means of a selective solvent, a mixture of C.sub.4 -hydrocarbons which contains some hydrocarbons which are more soluble in the selective solvent and some which are less soluble therein, in which process the hydrocarbon mixture is separated, in an extractive distillation zone, into a top product which contains the less soluble hydrocarbons and an extract which contains the more soluble hydrocarbons and the selective solvent, the extract, taken off as the bottom product, is subjected to a flash evaporation and the resulting vapor component of the extract is recycled to the extractive distillation zone while the liquid phase remaining after the flash evaporation is fed to a solvent recovery zone, in which the liquid phase obtained from the flash evaporation is separated into a product containing the hydrocarbons and, as the bottom product, the selective solvent which has been freed from the hydrocarbons, the resulting selective solvent is recycled to the extractive distillation zone and the product which is obtained from the solvent recovery zone and contains the hydrocarbons is partially or completely recycled to the extractive distillation zone, after increasing the pressure in a compression zone, in which process the extract taken off the extractive distillation zone is brought, prior to the flash evaporation to a higher pressure than the pressure in the extractive distillation zone and thereafter the extract which is under this higher pressure is heated, in a heat exchange zone, by indirect heat exchange with the selective solvent obtained as the bottom product from the solvent recovery zone, and the heated extract is subsequently let down, in the flash evaporation, to a pressure which is at least equal to the pressure in the extractive distillation zone and is higher than the pressure in the solvent recovery zone.

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Wachenheim, Germany

Detlef Bender