Studies of the Kinetic and Thermodynamic Parameters of Levulinic Acid in the Conversion to Ethyl Levulinate via Esterification Catalysed by Sulfonated Food Waste Char

This work investigated the kinetics and thermodynamics of levulinic acid (LA) conversion to ethyl levulinate (EL) catalysed by sulfonated food waste char (SFC) catalyst. The food waste char was derived from the hydrothermal liquefaction of food waste that underwent sulfonation with sulphuric acid to prepare an acid-functionalised catalyst. The esterification reaction was performed by varying the process parameters, including catalyst particle size (300 and 600 μm), agitation speed (100 and 300 rpm), reaction time (1–4 h), and heating temperature (60–80 °C). The EL yield and LA conversion were determined through the concentration of the respective chemicals analysed by gas chromatography-mass spectrometry. Pseudo-homogeneous kinetic models were employed to determine the reaction order and kinetic parameters. Subsequently, the thermodynamic parameters were determined using the Eyring equation. Based on the results, the pseudo-first-order model was identified as the best-fit model to represent the reaction kinetics, yielding an activation energy of 56.1 kJ/mol, an enthalpy of activation of 52.3 kJ/mol, an entropy of activation of -190.9 J/mol·K, and a Gibbs free energy of activation of 84.4 kJ/mol.