A kinetic study of biodiesel in waste cooking oil

Abstract

Methyl esters are produced by transesterification of waste cooking palm oil with methanol in the presence of a catalyst, potassium hydroxide (KOH). These reactions were carried out in 4:1 (molar ratio of methanol and oil) with 0.45 weight % of the catalyst used. The rate of reaction was enhanced with increasing temperature of 50, 55 and 60 up to 65°C, and for every temperature, three samples were taken with 10 min intervals. The concentrations of methyl esters in the collected samples were determined by gas chromatography method. The kinetic mechanism of second order system was plotted in graph between 1/[G] versus t and log K versus 1/T. This graph shows activation energy for both forward, reverse reactions and correlation constant for each point. The optimum values of the rate constants are 0.018 to 0.168 weight % per min for transesterification of biodiesel from various temperatures and the activation energies included 2.53, 1.93 and 1.29 Kcal/mol for final concentration of triglycerides (TG), final concentration of diglycerides (DG) and final concentration of monoglycerides (MG) hydrolysis reactions, respectively. These activation energy values are more effective to precede the reaction.

Key words: Biodiesel, kinetics, methyl esters, waste cooking oil, transesterification, gas chromatography.