Effect of Sodium Hydroxide On Biodiesel Production From Castor Oil Using Sub and Supercritical Ethanol

In this work, the effect of using Sodium Hydroxide (NaOH) as catalyst on the synthesis of Biodiesel from castor oil and ethanol under subcritical and supercritical conditions (200 °C to 350 °C at endogenous pressure) is studied. The influence of the operating variables: temperature, reaction time, ethanol:oil molar ratio and catalyst concentration (when used) on the reaction conversion was analyzed using designs of experiments along with the surface response methodology for both the catalytic and non-catalytic processes.  It was verified that using 0.1 % wt of NaOH, for the catalytic process, which is a lowest amount than the required to neutralize the oil, it is possible to obtain high conversions. The maximum conversion reached was 98.9 % for the catalytic process and 56.2 % for the non-catalytic process.  Additionally, the reaction kinetic was determined and it was found to be a pseudo first order reaction. Activation energies were calculated from the Arrhenius equation.