Mathematical modeling and experimental esterification at supercritical conditions for biodiesel production in a tubular reactor

The non-catalytic esterification of oleic acid with supercritical ethanol was carried out in a tubular reactor at different temperatures (150-300 degrees C), molar ratios (1:1-6:1) and volumetric flow rates (0.001-0.005 dm(3)/min). The highest free fatty acid conversion was obtained at 300 degrees C, ethanol to oleic acid molar ratio of 6:1 and fixed pressure of 150 bar. A phenomenological axial dispersion model was developed to evaluate the intrinsic effects of the operating variables on the conversion of oleic acid to ethyl oleate. The density of the reaction mixture was estimated using the Peng-Robinson equation of state. Distinct experimental data set were used for parameter estimation and validation of the model. The results demonstrated that the correction of the flow velocity is necessary, and that the axial dispersion effect cannot be neglected.