Continuous flow nitration of 3-[2-chloro-4-(trifluoromethyl) phenoxy] benzoic acid and its chemical kinetics within droplet-based microreactors

Aromatic nitration still faces unmet technical challenges in relation to being heterogeneous and highly exothermic. In this work, a continuous flow aromatic nitration was developed with mixed acid within droplet-based microreactors. The effects of key operating parameters were characterized on the nitration of 3-[2-chloro-4-(trifluoromethyl)phenoxy] benzoic acid. The optimized reaction temperature, M-ratio and N/S were found to be 308 K, 1.6 and 0.57, respectively. Under these conditions, a conversion of 83.03% and selectivity of 79.52% were achieved. The addition of acetic anhydride improved both the solubility of etherate in the organic phase and the absorbability of water produced from the reaction, leading to increase in conversion, however increased by-products accordingly with reduced selectivity. Pseudo-homogeneous kinetics models were developed of apparent and intrinsic reaction rate constant, supporting the second-order reaction assumption. The calculated results based on the kinetics model were found to be in good agreement with the experimental results.