Glycerin-Free Synthesis of Jatropha and Pongamia Biodiesel in Supercritical Dimethyl and Diethyl Carbonate

Abstract

To overcome the fear of glycerin glut formation based on biodiesel production process, the present study is aimed at investigation of glycerin-free biodiesel process under nonconventional synthesis conditions. Accordingly, glycerin-free synthesis of biodiesel from nonedible oils viz. jatropha and pongamia oils under supercritical conditions has been investigated with either dimethyl carbonate (DMC) or diethyl carbonate (DEC) as methylating agent. Typically, supercritical conditions with 40:1 molar ratio of DMC or DEC to oil at 325 °C/150 bar have been found to be adequate to achieve nearly complete conversion in 45 min. Furthermore, reaction kinetics has been investigated under supercritical conditions of DMC and DEC in the temperature range 250–350 °C at 150 bar. Estimated activation energies (Ea), are on the order of 38.0 ± 2 and 35.5 ± 2 kJ/mol for DMC and 40.4 ± 2 and 38.2 ± 2 kJ/mol for DEC, for conversion of jatropha and pongamia oils, respectively, with pseudo-first-order kinetics. The prepared bio...