Laser rapid-prototyping and modular packaging of chip-based microreactors for direct fluorination reactions

We have developed a laser rapid-prototyping method for the realization of microchannels and nozzles in silicon and nickel chips. A practical application of such microreactors, made by rapid prototyping, is the direct fluorination of organic substrates via microbubbles, a highly exothermic and chemically harsh reaction. By employing optimized laser raster ablation procedures, different channel cross-section shapes could be manufactured with adjustable channel wall angles. Modular compressive chip packaging allowed for safe reactor sealing without permanent chip-to-chip bonding. Fluorine gas was introduced into the microchannels, producing a monodisperse chain of bubbles (diameter ∼200 μm) with the reaction taking place at the gas/liquid interfaces. Successful direct fluorinations of fluoroethylene carbonate were carried out over 107 h at room temperature without noticeable leakage or corrosion. High reaction efficiency and an excellent space-time yield for the four products (4,4-F2EC: trans-F2EC: cis-F2EC: F3EC) was demonstrated (65% F2-usage, 1.41 × 106 mol m−3 h−1). cis- and trans-F2EC have shown great potential as electrolyte additives for increasing the lifetime of lithium ion batteries, and trifluorinated F3EC, with eventually improved characteristics, was for the first time fully characterized, e.g. by NMR spectroscopy.