Kinetic and thermodynamic approaches on biodiesel reaction in a simultaneously cooled enhanced microwave system

Abstract

Transesterification reaction kinetics of canola oil with calcined dolomite was investigated in an Enhanced Microwave System (EMS) which can work under constant, continuous microwave (MW) power and isothermal conditions. The kinetic data obtained at 65 °C were fitted into different order models depending on methanol-to-oil molar ratio (nm/no: 3–15) to estimate the most suitable kinetic model. For nm/no=9, the selected best kinetic model and reaction order with the first-order rate equation showed good fit with high correlation coefficients (R2) at different temperatures (50–65 °C) in EMS and Conventional Heating System (CHS). While the activation energy of 108.6 kJmol−1 and pre-exponential factor of 7.3x1013 min−1 were found in EMS respectively, these values were found to be lower as 24.2 kJmol−1 and 5.47 min−1 in CHS, respectively. The thermodynamic parameters (ΔG, ΔH ΔS) of the transesterification reaction were also investigated. The nature of the reaction was found non-spontaneous, endergonic, and endothermic due to positive values of ΔG, ΔH in both systems. Further, positive ΔS showed that randomness more increases in EMS than in CHS. It was seen that MW energy more effective on pre-exponential factor and thermodynamic parameters. Thus, the reaction occurred much faster in EMS than in CHS.