Synthesis of propyl benzoate by solvent-free immobilized lipase-catalyzed transesterification: Optimization and kinetic modeling.

The present study aimed to analyze reaction kinetics and mechanism for the synthesis of propyl benzoate in solvent-free conditions. Lipase was immobilized on Hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) polymer blend by entrapment method. Among different lipases immobilized on a support, Candida cylindracea (CCL) showed excellent activity. Systematic studies were done to optimize the reaction conditions. The activation energy was found to be 16.2 kcal/mol for immobilized CCL. Kinetic parameters were calculated, which depicted that propyl benzoate synthesized using immobilized CCL followed the ternary complex model in which propanol inhibits lipase activity at higher concentrations. Recyclability of the catalyst was checked up to four catalytic cycles and 40% retention of activity was observed up to the fourth cycle. Finally, the applicability of developed protocol to synthesize various alkyl benzoates was explored.