Three-phase reactor designs based on rotating solid foams for the application in the fine chemical industry are developed. The aim is to use solid foams both as a catalyst support and stirrer in order to mix the gas and liquid phases and create fine gas bubbles. Gas-liquid mass transfer data are presented for different solid foam stirrer configurations and compared to an optimized Rushton stirrer. Solid foam stirrers were developed in a blade and a block design. Both foam reactor designs work at stirring rates below 600 rpm. Using the foam blade design, gas bubbles are mainly created by the turbulence at the gas-liquid interface. Large bubbles are broken up by the foam blades. Using a foam block design, rotation leads to the structurization of the reactor volume into sections strongly differing in gas holdup, flow behavior and bubble size distribution. This results in a gas-liquid mass transfer, which is 50% higher than the Rushton stirrer used as comparison. The foam stirrer designs can be easily used in ordinary three-phase reactors and show a high potential for further optimization of the gas-liquid flow pattern and therefore for further increase of the rate of mass transfer. (C) 2009 Elsevier Ltd. All rights reserved.