Keys for Bioethanol Production Processes by Fermentation and Ionic Liquid Extraction

© 2017 American Chemical Society. Bioethanol is produced by fermenting biomass. However, the main drawback of this process is the high purification costs involved, which are due to the energy-intensive distillation step and a drying step if high ethanol purity is required. This work evaluates an alternative separation-purification process for the production of ethanol, in which an ionic liquid is used to develop an integrated extraction-fermentation process. The capacity of ionic liquids to extract ethanol from an ethanol aqueous solution and their biocompatibility with Saccharomyces cerevisiae was analyzed. Ethanol extraction percentages ranging from 33% to 62% were obtained with the following water insoluble ionic liquids: [EPy+][NTf2 -] < [MTOA+][NTf2 -] < [OMIM+][BF4 -] < [Hex3TDP+][dca-] < [Hex3TDP+][Br-] < [ Hex3TDP+][Cl-]. These ionic liquids could be used for in the postfermentation step of extraction. To evaluate the potential use of these ionic liquids as extraction phase in an integrated reaction/separation process, their biocompatibility with S. cerevisiae was analyzed. Of the above ionic liquids, [MTOA+][NTf2 -], [BMIM+][NTf2 -], [OMIM+][NTf2 -], [BMIM+][PF6 -] and [Hex3TDP+][Cl-] were found to be biocompatible with S. cerevisiae because they allowed bacterial growth. From the extraction and biocompatibility tests, it can be concluded that [MTOA+][NTf2 -] and [Hex3TDP+][Cl-] would be suitable for an integrated extraction-fermentation process for ethanol production.