The objective of this work is to use numerical simulations to show how bubble (size and shape) and particle properties can influence the selectivity of fast heterogeneously catalyzed gas-liquid reactions. For fast gas-liquid-solid reactions. the reaction occurs primarily in the wake of the bubble and is thus dependent only on the mixing in this region. This work investigates how the wake structure changes for different bubble shapes and how catalyst particles distribute for different Stokes number particles. Finally, the results of this work will be applied to two industrially relevant reaction systems to show how choosing the correct design and operating parameters of a system can significantly influence the selectivity of fast heterogeneously catalyzed gas-liquid reactions, (c) 2005 American Institute of Chemical Engineers.