Unraveling the Role of Fluid Shear on Primary Nucleation of Paracetamol through an Energy-Dissipation Rate Analysis

The effect of fluid shear on the primary nucleation of paracetamol in water, isopropyl alcohol, and acetonitrile was investigated. First, experiments were performed with a Taylor-Couette crystallizer. For all three solvents, a comparable effect of fluid shear on the nucleation kinetics was found: increasing fluid shear results in an increase in the nucleation rate and a decrease in the variability of the induction times. The experimental analysis shows that the mean induction times are dependent on the energy dissipation rate to a power of approximately -1/3. A comparative investigation for paracetamol crystallization in stirred batch crystallizers revealed the same dependence of mean induction times on the energy dissipation rate. Extending this analysis to experimental data sets from the literature confirms this further. To find a physical meaning for this dependency, the results are interpreted in terms of the shear-enhanced mass transfer and shear-enhanced cluster aggregation theories.