Process optimization, kinetic and thermodynamic studies on biodiesel production by supercritical methanol transesterification with CH3ONa catalyst

摘要

This study provided a novel supercritical methanol transesterification process with little amount of CH3ONa catalyst to synthesize biodiesel from soybean oil by response surface technology. The maximum biodiesel yield was 97.42% under the optimal conditions of 250 degrees C, methanol to oil molar ratio of 23: 1, 1.0 wt% CH3ONa and 20 min. Temperature was proved to have the most significant effect on transesterification, followed by methanol to oil molar ratio and catalyst amount. The kinetic model suggested a 1.5th order reaction with the activation energy of 27.06 kJ.mol(-1) and the pre-exponential factor of 102.71. The values of thermodynamic parameters including enthalpy, entropy and Gibbs free energy for this process were calculated as 23.15 kJ.mol(-1), -0.22 kJ.mol(-1).K-1 and 137.43 kJ.mol(1) at 250 degrees C, respectively. Reduced reaction temperature, catalyst amount, and reaction time are among the advantages of the integrated process for biodiesel production over single supercritical process and conventional catalytic methods. (C) 2017 Published by Elsevier Ltd.