Advancing the organosolv biorefinery. Part I: Vapor stripping–vapor permeation for the recovery of 1‐butanol from aqueous solutions

Abstract The industrial implementation of many lab‐scale biorefinery designs has been significantly hampered by the lack of availability of efficient and cost‐effective chemical recovery techniques. This is of particular importance for organic solvent‐based biorefineries such as those that use or produce aqueous butanol–water streams which, based on phase equilibrium, may contain up to 7 wt% butanol. Vapor stripping–vapor permeation (VSVP), a variation of pervaporation with a vapor phase feed, has emerged as a promising approach for butanol recovery from dilute aqueous solutions. It combines the butanol‐enriching properties of vapor stripping with a vacuum‐driven organophilic membrane separation. The impact of feed temperature, feed vapor flow rate, and temperature offset between the feed and membrane were investigated to evaluate their effects on VSVP performance and determine optimal operating conditions. Fluxes were found to increase with both feed temperature and feed vapor flow rate, while permeate butanol concentration was found to remain largely constant at an average of 72 wt% butanol. The best operating conditions for butanol recovery were found to be a feed temperature of 80 °C, a membrane temperature of 70 °C, and a feed vapor flow rate of 3.0 L min −1 . Under these conditions, the minimum membrane area required to reduce the butanol concentration from 7 to 1 wt% in a model aqueous phase generated from processing 1 metric tonne of biomass per hour was calculated to be 87 m 2 . This work demonstrates great potential for the use of VSVP to perform butanol recovery from aqueous solutions.