Microwave-assisted heterogeneous esterification of dibutyl maleate: Optimization using response surface methodology

Abstract

Microwave-assisted synthesis of dibutyl maleate was carried out with heterogeneous catalyst, Amberlyst-15. Effect of process parameters such as mole ratio, reaction temperature, catalyst loading, and molecular sieves on the conversion was reported using Response Surface Methodology (RSM). Reaction conversion of 62.6% was achieved at optimum parameters of 1:3 acid to alcohol mole ratio, 5.5% (w/w) catalyst loading, 70°C temperature, and 6% (w/w) molecular sieves for reaction time of 60 min. The optimum parameters based on RSM were 1:3.14 acid to alcohol mole ratio, catalyst loading 5.35% (w/w), 77.19°C, and 64.77% predicted conversion. Pseudo- Homogeneous (PH), Eley Rideal (ER), and Langmuir Hinshelwood Hougen Watson (LHHW) models were used to fit experimental kinetic data. Studies revealed that the Eley-Rideal model suited the experimental data. The activation energy of the esterification reaction was calculated as 10.17 kJ/mol. Gibbs free activation energy (ΔG‡), enthalpy of activation (ΔH‡), and entropy of activation (ΔS‡) were evaluated.