The impact of microfluidic reactor configuration on hydrodynamics, conversion and selectivity during indan oxidation

Abstract

The effect of microfluidic reactor dimensions and cross section geometry on hydrodynamics, conversion and selectivity was studied for gas-liquid two-phase flow reactors. Indan oxidation at 100–160 °C and 300 kPa O2 was employed to study the impact of hydrodynamics on conversion and product selectivity. Microfluidic reactors of different dimensions and cross-section geometries were employed, 62.5 μL of irregular (half-elliptical) shape (Reactor A) and 1000 μL of rectangular shape (Reactor B). An in-depth mass transfer analysis was performed for the two reactors. For the same operating parameters of flow rate, temperature and pressure, a higher gas-liquid interfacial area was obtained with Reactor A than Reactor B. The configuration of Reactor A also resulted in better mixing than in Reactor B. These differences affected the free radical oxidation chemistry differently. At none of the conditions studied was oxygen transport from the gas to the liquid phase limiting. Indan conversion was dependent on gas–liquid interfacial area per unit volume, which caused Reactor A to achieve higher conversion than Reactor B at otherwise similar operating conditions. Product selectivity depended on oxygen availability in the bulk liquid. Poorer mixing in Reactor B caused the product from Reactor B to exhibit selectivity behavior typical of both high local oxygen availability (high ketone-to-alcohol ratio and higher selectivity to secondary products), and low local oxygen availability (addition products). The study demonstrated how reactor engineering could be used to independently control the conversion and the selectivity during liquid phase free radical oxidation chemistry.