Membrane assisted reactive distillation for bioethanol purification

Reactive distillation and membrane assisted reactive distillation have been considered as possible alternatives to extractive distillation for the concentration of ethanol from diluted streams. Aquaporin-based biomimetic forward osmosis membranes have been tested for ethanol tolerance and ethanol rejection. The experimental results were used to construct the process simulations developed in Aspen Plus. Different alternatives were proposed where the pre-concentration step was performed by membrane stand alone or a combination of membrane and ordinary distillation. In all the configurations reactive distillation using ethylene oxide was considered to reach the ethanol final concentration of 99.9 wt%. Ethanol recovery, energy consumed per kg of ethanol produced, total annual cost and economic analysis were used to compare the alternatives. It was obtained that ordinary distillation coupled with reactive distillation is at the moment the only alternative competing with extractive distillation. However, the sequence of membranes, ordinary distillation and reactive distillation has clear potentials to compete with the stand-alone distillation processes once the solutions for draw recovery and minimization of ethanol lost will be available.