(400c) In-Situ Isobutanol Recovery From An Autotrophic Fermentation in a Bioreactor for Incompatible Gases

In-situ Isobutanol Recovery from an Autotrophic Fermentation in a

Bioreactor for Incompatible Gases

For presentation at 2013 Annual American Institute of Chemical Engineers Conference, November 3-8, 2013

Soumen K. Maiti, Yangmu C. Liu, Carl T. Lira, and R. Mark Worden

Department of Chemical Engineering and Materials Science, Michigan State University

Isobutanol (IBT) is a drop-in biofuel that can be produced via heterotrophic fermentations on sugars or autotrophic “electrofuel” fermentations on H₂, CO₂, and O₂. Dilute aqueous solutions of IBT are highly non-ideal, with IBT exhibiting a substantially elevated relative volatility. We have recently developed a Bioreactor for Incompatible Gases (BIG) system that allows H₂ and O₂ to be simultaneously fed to IBT-producing cells without gas-phase mixing of the H₂ and O₂. The BIG generates both liquid and gas effluent streams, both of which may contain significant amounts of the IBT produced. The high relative volatility of the IBT vapor makes it difficult to condense completely without substantial refrigeration. An alternative method to recover the IBT vapor is adsorption onto an IBT-selective resin. Potential advantages of this approach are that it can be conducted at ambient temperature, and it can be used to recover IBT from both the gas and the liquid effluent streams. This paper describes studies to characterize recovery of IBT vapor from an air stream and dissolved IBT from a dilute aqueous stream. A styrene-based resin, Dowex Optipore SD-2 was found to effectively adsorb IBT from both gas and liquid streams of fermentation media at room temperature. Ethanol and methanol were effective desorbents, allowing nearly 100% IBT recovery from the resin. Methanol has the advantages of being less expensive and can be readily separated from the IBT via distillation. Reusability of resin has also been confirmed by using same resin for 20 times. This adsorption-desorption approach was used for in-situ recovery of IBT during autotrophic IBT production in the BIG system. A mathematical model describing IBT adsorption in a packed-bed column was developed to aid in process optimization and scale up.