BIODIESEL PRODUCTION USING SUPERCRITICAL ALCOHOLS IN BATCH AND CONTINUOUS REACTORS

P. VALLE; A. VELEZ; P. HEGEL; G. MABE; E. A. BRIGNOLE

Philadelphia, Pensilvania, USA

Encuentro; AICHE Annual Meeting & Centenial Celebration; 2008

In the present work the optimization of operating conditions in batch reactor for biodiesel production with supercritical alcohols and Raphanus sativus L. oil was carried out. This optimization is based on a statistical design of experiments for the construction of empirical models by the least square method. The key process variables were studied over different ranges to obtain a reliable model for the efficiency of the reaction as a function of reactants residence time, temperature, pressure and molar ratio of ethanol/oil. A Doelhert design of experiments was utilized to obtain a response surface and to optimize the reaction conditions in the studied range of the variables. The reactor phase transitions were directly observed in a double windowed cylindrical reactor and the conversion to ethyl esters was measured by gas chromatography techniques. The results of this study show that high conversions from oil to ethyl esters can be achieved with temperatures between 570 and 600 K, and reaction time over 20 minutes, with a molar ratio ethanol/oil of 42/1. The global density of the system is constant for all batch experiments, and it has a value of 0,61 g/cm3. The range of pressure values for these experiments was 10-15 MPa. Also studies on a continuous reactor are carried out to obtain a better control of operating conditions and reactants residence time. High ester content (95%) was obtained when optimum conditions for transesterification reaction in batch experiences were used in continuous reactor with sunflower oil and ethanol. From direct observations and the modelling of the phase behaviour, a better understanding of the supercritical ethanol transesterification process is obtained as well as the confirmation of the phase equilibrium predictions based on the GCA-EOS model.