Design of energy-efficient ionic liquid-based extractive distillation systems for ethanol dehydration including alternatives for ionic liquid recovery

Designs of extractive distillation systems for ethanol-water separation using ionic liquids as entrainers are presented. Distillation sequences that integrate the extractive column with five options for ionic liquid recovery were designed. Two types of ionic liquids, namely, 1-butyl-3-methylimidazolium chloride [BMIM](Cl)] and 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM](BF₄)], were considered. Once initial designs were obtained, simulations using the Aspen Plus environment were conducted to identify the operating conditions of the separation sequences that minimize energy consumption. The designs were tested under two levels of IL flows, one with the minimum flow required for the separation and another one with the flows that minimized the total annual cost of the extractive column. From the total of 20 design options, it was found that the most energy efficient design was based on a low flow of [BMIM(Cl)] as entrainer, with an extractive column followed by a desorption column and a membrane unit for IL recovery.