Continuous microwave-assisted in-situ transesterification of lipids in seeds of invasive Chinese tallow trees (Triadica sebifera L.): Kinetic and thermodynamic studies

Abstract Continuous in-situ transesterification of Chinese tallow tree seeds into methyl esters using a resonant focusing cavity microwave coupled with a CSTR system was investigated. High production yield of 90% with 97% conversion rate was obtained in 24 min CSTR residence time at a methanol/hexane/Chinese tallow tree seed mass ratio of 47.5:39.3:20, a continuous microwave heating power of 290 W and 14 s exposure time, reaction temperature of 60 °C in presence of sodium hydroxide catalyst (4 g NaOH per 100 g oil). The experimental data fits first order reaction kinetics. The values of rate constants at different temperatures and the corresponding activation energy were found out to be 0.08–0.084 min −1 and 2057.4 J mol −1 , respectively. Thermodynamic parameters values such as Gibbs free energy ( ΔG ), enthalpy ( ΔH ) and entropy of activation ( ΔS ) were also determined. The positive values of ΔG and small negative value of ΔH indicated that the reaction has an unspontaneous/endergonic nature and is slightly exothermic.