To improve the selectivity and yield of multiphase reactions, an attempt to intensify gasliquid mass-transfer operations was undertaken in which screen/grid static mixers were used to promote interphase mass transfer. A modified technique was used to enhance the reproducibility of the results and to account for the depletion effect which becomes critical at high mass-transfer rates. The volumetric mass transfer coefficient, k(L)a, was found to increase with increasing liquid superficial velocity and gas volume fraction and reached values as high as 4.08 s(1) at low specific energy consumption rates, particularly for slowly coalescent systems, a situation that is encountered in most industrially relevant systems. The gasliquid reactor/contactor presently investigated takes advantage of the coalescence retardation characteristics of most industrially relevant streams to achieve k(L)a values that surpassed those of most conventional reactor/contactors by more than an order of magnitude while maintaining a high energy utilization efficiency (up to 0.63 kg O-2/kWh). The ability to reach 98% equilibrium within residence times of less than 800 ms, achieved without significantly increasing the power consumption rates, allows for the use of static mixing reactor volumes that are several orders of magnitude smaller than conventional units such as mechanically agitated tanks and bubble columns.