Kinetics of microwave-assisted synthesis of ethyl hexanoate by using heterogeneous catalyst: process intensification and energy consumption analysis

Abstract

The current work illustrates microwave-assisted synthesis of ethyl hexanoate without a solvent system using cationic resin (Amberlyst-15) as a catalyst. The effect of various parameters was evaluated, and a maximum equilibrium conversion of 84.2% was achieved in 50 min. The optimized parameters were 1:02 mole ratio of acid to alcohol, temperature 328 K, and 9% (w/w) catalyst loading. The impact of mole ratio and catalyst loading on the reaction rate was predicted by developing an empirical correlation. The activation energy was determined as 17.63 kJ/mol. The experimental data fitted well with Eley-Rideal mechanism, in which the surface reaction was a rate-limiting step. Thermodynamic parameters were evaluated, including standard enthalpy, Gibbs free energy, and reaction entropy. The energy consumption for microwave reaction was predicted as 15.357 × 105 kJ/kg. These results have been compared with that of conventional as well as ultrasound-assisted synthesis of ethyl hexanoate. This novel technique shows an enhancement in reaction rates and higher yields.