The technology of aqueous multiphase catalysis provides an economically beneficial and environmentally friendly approach for the application of homogeneous catalysis on an industrial scale. Its unique features make it possible to reduce the catalyst separation and recycling step, which is normally very complex, to a simple phase separation. Nevertheless, because of the complexity of such multiphase reaction systems comprising two liquid and a gaseous phase (Gas/Liquid/Liquid) a detailed reaction engineering analysis is very sophisticated and therefore until now carried out just for a few reactions. Reaction engineering aspects, especially the interaction of mass transport and reaction is yet not fully understood. However, in order to optimise the performance of a reactor or to scale up a laboratory plant to an industrial production plant, the results of these investigations are of special interest. Based on a model reaction system (selective hydrogenation of a,b-unsaturated aldehydes to the corresponding unsaturated alcohols by a watersoluble Ru-TPPTS-complex) the present PhD thesis provides methods and innovative reactor concepts, by which reaction engineering aspects in multiphase systems with a special focus on the interactions of mass transport and reaction can be analysed. With the aim of studying the impact of hydrodynamics on the mass transport rate a new and continuously operating loop-reactor was built up, by which the model reaction system could be carried out at conditions similar to those in industry. Thereby, the reaction was consciously investigated in a mass transport limited regime concerning the mass transport at the Liquid/Liquid-boundary layer. Results obtained with this loop-reactor and at these reaction conditions led to a deeper understanding of the impact of hydrodynamic parameters, such as mixer geometry or the volume rate, on the mass transport. The effect of the latter one could be additionally quantified by a kinetic model, which takes into account the mass transport and the intrinsic reaction rate as well. Reactions in multiphase systems can be carried out in micro-reactors with high mass transport rates, although the Re-number of the fluid phases are very low. This phenomenon can be explained in terms of the Taylor-flow characteristics of multiphase flows in micro-scaled channels. In the present PhD thesis a micro-reactor based on a micro-capillary as reaction zone was constructed and built up, which is specially designed for the investigation of Gas/Liquid/Liquid-multiphase reaction systems. The results obtained demonstrate, to which degree the effect of the Taylor flow can be influenced specifically by varying the volume rate or the internal capillary diameter. To summarize, the present PhD thesis contributes to a better and deeper understanding of reaction engineering aspects in aqueous multiphase catalysis by detailed kinetic investigations. Thereby, this knowledge is not only limited to conventional laboratory reactors, but can also be adapted to micro-dimensioned reactors.