Novelties of low energy microwave-irradiated tri-liquid phase transfer catalysis (MILLL-PTC): halo-exchange of benzyl chloride with sodium bromide

Abstract

In situ halogen exchange is witnessed in many organic reactions before the actual species participates in the main reaction. The aim of this work is to analyse the synergistic effect of microwave irradiation on tri-liquid phase transfer catalysed halo-exchange reaction between sodium bromide and benzyl chloride (BnCl) with tetra-butyl ammonium bromide as a catalyst. There is a process intensification leading to savings on reactor volume and processing costs. There is also waste minimisation since the catalyst phase is reused. The effects of various parameters such as mass transfer resistance, catalyst loading, mole ratio, temperature and reusability of third catalyst phase have been studied to provide an insight into the mechanism and kinetics of the reaction. A kinetic model has been developed and validated against the experimental data. The overall order of reaction is first order in BnCl. The values of apparent energy of activation and frequency factor were 23.0 kcal/mol and 1.03 × 10¹² kmol/(m³ s), respectively, for microwave irradiation and 20.19 kcal/mol and 1.27 × 10¹⁰ kmol/(m³ s), respectively, for conventional heating.