(350h) The Unusual Transport of Phenolic Compounds in Polymer Membranes

Bio-oil, a product of fast pyrolysis of biomass, contains numerous valuable chemicals and can be processed to a value-added energy source, such as biodiesel. Upgrading and refining bio-oil involves multiple energy-intensive steps. Moreover, many components of bio-oils are not thermally stable, which challenges the use of conventional thermally-driven separation techniques. Membrane-based separations are potential alternative technologies as the separations can be performed at low temperatures with energy-efficient mechanical pumping as the driving force. To investigate the membrane performance, we created a synthetic bio-oil from phenolic compounds, water, and alcohols. This liquid feed is permeated across a ~300 nm membrane, and the permeate is analyzed. Surprisingly, we observe that the phenolics (which are highly dilute) are preferentially permeated through the membrane and enriched in the membrane product. We observe that the flux of components in these systems is highly coupled, which allows the phenolic compounds to permeate “uphill” in terms of membrane driving forces. We explore the roots of this permeation coupling and identify ways in which the flux coupling can be engineered, leading to the unusual observation in the membrane separation that contradicts the traditional membrane modalities.