Droplet size and liquid-liquid mass transfer with reaction in a rotor-stator Spinning Disk Reactor

A liquid–liquid test reaction system involving mass transfer with competitive reactions was used to show the potential for Process Intensification of the rotor–stator Spinning Disk Reactor (rs-SDR) in comparison with batch operation in a Stirred Vessel (SV). Under the investigated conditions, the SV showed a dispersion of droplets of a Sauter diameter d ₃₂ between 120 and 75μm, while the rs-SDR achieved values between 35 and 2.5μm due to the high shear forces. In terms of selectivity towards the undesired product, X _S, the SV showed a decrease from 0.35 to 0.24 by increasing agitation, while the rs-SDR achieved values from 0.13 to 0.09. By modeling the system, the corresponding values for overall volumetric mass transfer coefficient k _La were one order of magnitude higher in the rs-SDR and as high as 0.24s ^-1. However, such values are much lower than the expected from the small droplet size. Literature suggests that the system is mass transfer limited, due to the formation of a monolayer of undissociated molecules around the interface. A model of diffusion with reaction is used to further model such effect. The model predicts well the product distribution experimentally obtained in the SV, although underestimates the values from the rs-SDR.