Solvents, despite their ubiquity in conventional multistep chemical processes, require energy- and cost-intensive removal and recovery steps (e.g., distillation) because of their inflexible physiochemical properties. Over the past decade, carbon dioxide (CO2)-triggered switchable hydrophilicity solvents (SHSs) have arisen due to their facile and reversible tuning of hydrophilicity, making them ideal candidates for liquid-liquid extraction, including extraction of algal biomass and bitumen. Despite groundbreaking research in the application of this exciting class of solvents, the mass transfer-limited conventional gas-liquid batch techniques (e.g., bubbling) have significantly hindered further adoption and utilization of SHSs in chemical industries. In comparison to batch techniques, microscale flow chemistry offers well-defined interfacial areas, enhanced mass transfer rates, and scalability via scale-out – making it a promising technique to study and optimize biphasic reactions at industrially-relevant throughputs. In this work, we present an intensified flow chemistry strategy using a scalable and reconfigurable microfluidic reactor for both accelerated screening of SHSs and high-throughput continuous extraction of CO2-triggered SHSs. Utilizing a tube-in-tube flow reactor with a gas-permeable Teflon AF2400 membrane and in-situ screening, optimization of the SHS extraction process was achieved in an order of magnitude faster with three orders of magnitude less chemical consumption than a conventional batch reactor. Optimized process parameters were directly implemented in a continuous flow strategy, achieving 12 times higher throughput than a batch reactor. Furthermore, the proposed strategies showed successful linear scalability with a scale-out approach consisting of three parallel flow reactors, offering 36 times higher throughput than a comparable batch process. The developed flow chemistry strategies in this work show comprehensive development of SHS from screening and optimization to high-throughput extraction and can be readily adapted to other switchable solvents.

CO2-triggered switchable hydrophilicity solvents: From accelerated screening to intensified continuous extraction

ACS Fall 2021

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