(262c) Flow Chemistry-Enabled Extraction Intensification of Switchable Hydrophilicity Solvents

Over the past decade, CO₂-triggered switchable solvents have emerged as promising candidates for energy-efficient solvent removal and recovery. The unique reversibility of switchable hydrophilicity solvents (SHSs) provides an ideal characteristic for green solvent recovery through liquid-liquid extraction and a wide range of applications such as extraction of algal biomass, bitumen, and aldol-condensation reactions.

Despite significant breakthroughs in the application of SHSs in various fields, the time- and material-intensive nature of conventional batch reactors have limited further development and exploration of SHSs. While conventional flask-based batch systems provide the relative ease and simplicity, studies of a gas-liquid process in a batch reactor are complicated significantly by poorly defined interfacial area (e.g., bubble column offers 50-600 m²/m³) and small mass transfer coefficient (e.g., bubble column provides 0.005-0.025 s^-1). On contrary, Microscale multi-phase flow strategies offer unique characteristics (e.g., intensified and tunable mass and heat transfer rates, precise tuning of process parameters), dramatically accelerating fundamental and applied studies of gas-liquid processes. Utilizing a highly gas-permeable membrane in a tube-in-tube configuration, the microfluidic reactors can provide a significantly higher interfacial area (~5000 m²/m³) and mass transfer coefficients (0.1-1 s^-1) than a batch reactor.

In this work, we developed a intensified continuous flow strategy for continuous extraction of SHSs, utilizing the reconfigurable nature of a tube-in-tube microfluidic reactor.We demonstrated the facile scalability of SHS extraction from a single-droplet to a continuous flow reactor through the utilization of a similar tube-in-tube flow reactor geometry. With optimized process conditions enabled by an in-situ image-based characterization technique, the continuous flow reactor achieved an SHS extraction throughput 12 times higher than a batch reactor and demonstrated linear scalability by a scale-out approach. The developed flow chemistry platform in this work can readily be adapted for accurate fundamental studies and intensified extraction of other types of switchable solvents.