Kinetics and thermodynamics of lipase catalysed synthesis of propyl caprate

To investigate kinetics and thermodynamics of lipase-catalyzed esterification of capric acid with 1-propyl alcohol in a solvent-free system for synthesis of propyl caprate.

The capric acid conversion of 83.82% is achieved at temperature 60 °C, speed of agitation 300 rpm, molar ratio acid:alcohol 1:3, enzyme loading 2% (w/w) and molecular sieves loading 5% (w/w). The activation energy (Ea) for the reaction was determined as 37.79 kJ mol^-1. Furthermore, enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG) values were found out to be + 90.45 kJ mol^-1, + 278.99 J mol^-1 K^-1 and - 2.35 kJ mol^-1 respectively.

The results showed that the lipase-catalyzed esterification exhibits an ordered bi-bi mechanism with capric acid inhibiting the reaction and forming the dead-end complex with the lipase. Under the given set of reaction conditions, the lipase catalysed esterification reaction was anticipated to be spontaneous, referring to the value of the Gibbs free energy change (ΔG). Moreover, the esterification process was found to be endothermic, based on the values of enthalpy (ΔH) and entropy (ΔS).