Bicontinuous Biphasic Liquid Emulsions for Catalysis and Separations

Daeyeon Lee, Chemical & Biomolecular Engineering, University of Pennsylvania, Philadelphia, United States

A recent approach that has shown great promise for biomass conversion and biofuel upgrade reaction involves using biphasic emulsions stabilized with interfacially active catalytic nanoparticles. This novel methodology combines the advantages of phase transfer and heterogeneous catalysis. One drawback that limits the widespread utilization of this approach, however, is that catalyzed reaction and separation cannot be performed in a continuous mode. To enable continuous reactions and separations in a biphasic liquid mixture, we explore the formation of bicontinuous interfacially jammed emulsions (Bijels). Bijels are typically prepared by arresting spinodal decomposition of two fluid phases via interfacial attachment and jamming of colloidal particles. Their fabrication is currently limited to a few pairs of immiscible liquids, and bicontinuous morphology can be obtained within narrow composition and temperature windows, potentially limiting their use in reactions involving a specific combination of reaction/separation media, catalytic nanoparticles and reaction temperature. We explore the formation of bijels by solvent transfer-induced phase separation (STRIP) of ternary mixtures. The use of commercially available silica nanoparticles and ionic surfactants allows us to continuously form bijel fibers with controllable morphologies and domain sizes down to a few hundreds of nanometers. We study the dependence of fiber morphology on different control parameters such as particle and surfactant concentrations. We also develop a new in situ technique to characterize the mechanical properties of bijel fibers during different stages of their maturation. Our recent work on using bijel-derived systems for membrane separation and reactive separation will be introduced.