The characteristics of an intermeshing co-rotating twin screw extruder were investigated as a three-phase reactor using a model reaction. The kinetics of the reaction and base line data were obtained using a high pressure stirred tank reactor. The feasibility of immobilisation of palladium on the surface of the screws as the catalyst was also studied. The behaviour of the extruder in batch and continuous mode and with slurry and non-slurry solutions was investigated. The results confirmed the superiority of the intermeshing co-rotating twin screw extruder as a novel three-phase reactor compared to the stirred tank reactor as a traditional three-phase reactor. The residence time distribution measurements indicated that the behaviour of the extruder approached perfect plug flow reactor with increasing viscosity of reaction solution.