Microstructured reactors are known to provide high heat and mass transfer rates for liquid–liquid twophase systems when used as a single channel. For industrial scale production, scale-up of microstructured reactors is essential to achieve throughput in the required range which is done by numbering-up of a single channel. The important issues are uniform flow distribution and identical slug size in all channels. In the present work, a capillary microstructured reactor is numbered up for six capillaries and the mass transfer performance is investigated for various operating conditions. A cationic surfactant was used to study the effect of interfacial tension on the mass transfer performance. If compared to conventional contactors, the mass transfer coefficients were approximately one order of magnitude higher allowing the process intensification. The results obtained demonstrate the benefits of microstructured reactors and confirm that the throughput of conventional reactors can be achieved.