Abstract: A reactor for carrying out gas/liquid/solid phase reactions, comprises a housing (1) which encloses an essentially closed reaction chamber (2) for holding a first liquid phase, the solid phase and a gas phase fed through the chamber; at least one feed (3), connected to the reaction chamber, for feeding a first liquid phase to the reaction chamber (2); at least one hollow fiber (4), the wall of which defines an internal flow channel for at least removing a second liquid phase, such that exchange of matter can take place between the reaction chamber (2) and the flow channel through the wall of hollow fiber (4); at least one discharge (6), connected to the flow channel, for removing the second liquid phase; at least one gas inlet (7) and at least one gas outlet (8), connected to reaction chamber (2) such that, in the use position, the at least one gas inlet (7) opens essentially into the bottom of the reaction chamber (2) and the at least one gas outlet (8) is located essentially at the top of the reaction chamb