Mass transfer and hydrodynamic analysis in triphasic aerobic epoxidation of limonene over Ru/ activated carbon

• Gas-liquid-solid reaction • External mass transfer • Hydrodynamic analysis • Direct aerobic epoxidation • Biomass derived liquids This study investigates mass transfer in a triphasic stirred tank reactor during the aerobic epoxidation of limonene using Ru supported on activated carbon as a heterogeneous catalyst. The volumetric gas-liquid mass transfer coefficient (k L a) was determined via the dynamic absorption method, based on oxygen uptake, referring to Danckwerts surface renewal model. Hydrodynamic parameters, including power input and Reynolds number were calculated to characterize the flow regimes, while bubble diameter and gas holdup were estimated to evaluate the interfacial area available for mass transfer. The Kolmogorov length scale was found significantly larger than the catalyst particle diameter, indicating negligible contribution of solid phase in the fluid carrier hydrodynamic conditions. Additionally, the Weisz-Prater number was much lower than one, confirming the absence of internal mass transfer limitations within the catalyst. Results demonstrate that increased turbulence enhances interfacial area and improves mass transfer, due to intensified bubble breakup, underscoring the importance of hydrodynamic control in optimizing catalytic aerobic epoxidation.