Hybrid distillation-pervaporation in a single unit: Experimental proof of concept in a batch operation

In a Distillation-Pervaporation in a Single Unit (DPSU) system, the pervaporation unit is located inside a distillation column. Therefore, distillation and pervaporation mechanisms are carried out simultaneously in the same column section. Previously, it was theoretically demonstrated that a DPSU column is able to overcome azeotropic conditions by displacing the liquid composition due to the pervaporation. In this work, this behaviour is experimentally verified for a DPSU system in a batch operation for the separation of ethanol – isopropanol – water mixture, using a silica membrane selective to water. Several feed compositions and permeate pressures were evaluated to identify their effects on the DPSU separation performance. The distillation boundary was experimentally overcome by the DPSU system. The separation order of isopropanol and water was inverted in the DPSU system as compared to conventional distillation. Water became a saddle point for the entire composition space, allowing crossing the distillation boundary with a continuous composition profile of the residue liquid. This study experimentally proves the validity of the DPSU approach for azeotropic mixture separations.