Advancing Rare-Earth Elements Separation: Continuous Flow Synthesis of Diglycolamides

Diglycolamides (DGAs) are crucial ligands for the separation of rare-earth elements (REEs). Traditional batch methods for synthesizing DGAs are labor-intensive, requiring multiple steps with manual intervention, often limited by heat and mass transfer inefficiencies. In contrast, continuous flow synthesis leverages controlled, automated operations that allow for efficient, scalable, and sustainable production.
The setup of a continuous flow reaction set up includes components such as piston pumps for precise reactant delivery, a quad mixer for uniform mixing, a coil reactor for sustained reaction, and inline analytical tools, such as infrared (IR) spectrometer for real time reaction monitoring. The reaction system is automated via Rxn Rover software, facilitating real-time adjustments and reaction monitoring. This setup enables the adjustment of various reaction parameters, including temperature, pressure, and reactant equivalents, supporting high yield optimization. Reaction mixture solutions of dimethyl 2,2'-oxydiacetate and xylene with the addition of a dialkyl amine were tested. Several dialkyl amine reactions at 8 equivalents were observed at temperatures, ranging from 180℃ to 280℃ for 90 minutes at each temperature.
The continuous flow reaction setup enabled expanded substrate testing, proving effective across different dialkyl amines. This approach demonstrates significant potential for enhancing the production efficiency of DGAs, offering a path towards greener and more efficient chemical manufacturing solutions for REE separation applications.