Flow distribution and ozonolysis in gas-liquid multichannel microreactors

Multichannel microreactors for gas-liquid reactions are designed and fabricated using silicon and Pyrex wafers. We perform oxidation of organic reagents by ozone (ozonolysis) in these microreactors motivated by the difficulty of handling ozone, its high reactivity, the potentially high selectivity for oxygenated products, and the reaction often being mass transfer limited. Pressure drop zones are included in the microreactors to achieve a uniform gas-liquid flow regime across the multiple channels. Flow visualization experiments show less than 3% variation in mass flow across the channel for a range of operating conditions. Microfabricated silicon posts are included in the channels as a means to increase mass transfer, and their effectiveness is evaluated by comparing conversion and selectivity to those obtained for microreactors without posts. Oxidations with ozone of phosphite, amine, and olefin as model compounds serve as case studies. In all cases, both conversion and selectivity are high, up to 100% at short contact times as low as 1 s.