Advances on kinetics and thermodynamics of non-catalytic supercritical methanol transesterification of some vegetable oils to biodiesel

•Kinetic study of non-catalytic scMeOH reaction was evaluated for some vegetable oils.•Thermodynamic study of non-catalytic scMeOH reaction was performed for some vegetable oils.•Pseudo-first-order equations were appropriate to describe the scMeOH transesterification.•The reaction rate can be correlated to the content of linolenic acid in the oil.•Non-catalytic scMeOH reaction of vegetable oils is endergonic and endothermic in nature. Kinetic and thermodynamic parameters of the non-catalytic supercritical methanol transesterification reaction of castor, jatropha, pongamia, tobacco, soybean and jojoba oils to biodiesel production were evaluated in the present study. The experiments were conducted in an 83 ml closed batch reactor at different temperatures (250–350 °C) and reaction times (15–90 min), and at optimal methanol-to-oil molar ratios (15:1 in the case of jojoba wax-oil and 43:1 for the rest of the oils). The pressure reached in the reactor ranged from 10 to 43 MPa. Integral method was used to determine appropriated reaction orders by an adjustment of experimental data to pseudo-zero, pseudo-first and pseudo-second order kinetic equations using Levenberg-Marquardt algorithm. Pseudo-first-order kinetic equation was found to be the most appropriate to describe the supercritical transesterification reaction of the vegetable oils studied. Rate constants and Arrhenius parameters were calculated, the activation energy followed the sequence: castor oil