Kinetic Studies on Oxirane Cleavage of Epoxidized Soybean Oil by Methanol and Characterization of Polyols

Abstract

Abstract The kinetics of the oxirane cleavage of epoxidized soybean oil (ESO) by methanol (Me) without a catalyst was studied at 50, 60, 65, 70 °C. The rate of oxirane ring opening is given by k [Ep][Me] 2 , where [Ep] and [Me] are the concentrations of oxiranes in ESO and methanol, respectively and k is a rate constant. From the temperature dependence of the kinetics thermodynamic parameters such as enthalpy (Δ H ), entropy (Δ S ), free energy of activation (Δ F ) and activation energy (Δ E a ) were found to be 76.08 (±1.06) kJ mol −1 , −118.42 (±3.12) J mol −1 k −1 , 111.39 (±2.86) kJ mol −1 , and 78.56 (±1.63) kJ mol −1 , respectively. The methoxylated polyols formed from the oxirane cleavage reaction , were liquid at room temperature and had three low temperature melting peaks. The results of chemical analysis via titration for residual oxiranes in the reaction system showed good agreement with IR spectroscopy especially the disappearance of epoxy groups at 825, 843 cm −1 and the emergence of hydroxy groups at the OH characteristic absorption peak from 3,100 to 3,800 cm −1 .