Parametric studies of methyl esters synthesis from Thumba seed oil using heterogeneous catalyst under conventional stirring and ultrasonic cavitation

Abstract

The depletion of petroleum resources has created great demand for environmental friendly renewable energy sources. Biodiesel is one of the alternatives to petroleum fuels. The objective of present study is to produce biodiesel (Thumba methyl ester) from Thumba oil in presence acidic ion exchange resin i.e. Amberlyst 15 catalyst followed by results of experimental investigation carried out by the conventional stirring method as well as an ultrasonic cavitation method. The effect of molar ratio (1:4 to 1:8 (oil to alcohol)), catalyst concentration (1.0–1.4% (Weight of catalyst/Weight of oil)), Reaction temperature (55 °C–70 °C) on yield of fatty acid methyl ester (FAME) and conversion of triglycerides (TG) were studied by keeping other process parameter constant. Many experiments were employed to investigate the effects of these parameters. Using conventional stirring method, More than 91% conversion of TG was obtained at optimum values of 65 °C in 1 h with 1:6 oil to methanol molar ratio and catalyst concentration of 1.2% Amberlyst 15 in oil. A higher yield of thumba methyl ester about 89% and conversion of triglycerides about 97% was obtained in ultrasonic cavitation reactor within 40 min only. The optimized values of temperature, oil to alcohol molar ratio and catalyst concentration were found to be 65 °C, 1:6 molar ratio and 1.2 wt% of oil respectively. Ultrasonic cavitation method was found to be more rapid, energy efficient and time saving over conventional stirring method. Thermodynamic parameters such as standard heat of reaction, standard Gibbs free energy change and equilibrium constant at optimized operating conditions were reported. A kinetic study of transesterification of Thumba oil for conventional heating method is presented in this paper. The observed rate constant for the overall reaction was of two orders. The experimental data thus obtained was well fitted to the second order kinetics with respect to methanol.