Synthesis of methyl benzoate intensified by p-toluenesulfonic acid-based deep eutectic solvents†

Abstract

Methyl benzoate (MB) is a chemical raw material used in various fields. However, the conventional approach to synthesizing MB is characterized by difficulties such as equipment corrosion, by-product generation, and recycling challenges. In light of these challenges, this work proposes the utilization of deep eutectic solvents (DESs) as both extractants and catalysts in a reactive extraction process. In particular, p-toluenesulfonic acid-based deep eutectic solvents (PTSA-based DESs) were tested as potential candidates, with choline chloride (ChCl) and imidazole (Im) chosen as hydrogen bonding acceptors (HBAs). The feasibility of DESs consisting of ChCl and PTSA was assessed using the COSMO-RS theory. The optimal process conditions were determined. Under the optimal conditions, the yield of MB reached 93.46%, and the performance of [ChCl–PTSA] remained stable after five cycles. We also used the group contribution method and COSMO-RS to derive separate kinetic models, with activation energies of 43.71 kJ mol⁻¹ and 38.71 kJ mol⁻¹. Our work highlights the potential of [ChCl : PTSA] in the industrial production of MB.