Volumetric Properties of Reacting Mixtures in Biodiesel Production with Supercritical Alcohols: Experimental Measurements and Correlations.

A. VELEZ; P. HEGEL; S. ESPINOSA; E.A. BRIGNOLE

Praia da Rocha, Portugal

Conferencia; VIII Iberoamerican Conference on Phase Equilibria and Fluid Properties for Process Design ? Equifase; 2009

Facultade de Engenharia - Universidade do Porto

In the current work the densities of vegetable oils + methanol reacting mixtures were measured by loading a closed vessel with a known amount of an oil/alcohol mixture of known molar ratio. The mixture is brought to a temperature above its critical temperature and the isochoric relation between temperature and pressure for this particular density and composition is recorded. In the temperature range studied 550 ? 630 K, the complete conversion of the oil to the corresponding fatty esters and glycerin is obtained. Under the isochoric conditions the densities of sunflower oil with methanol for two different alcohol/oil ratios: 40 and 25 were measured. Also densities of coconut oil + methanol and methyl oleate + methanol mixtures were measured. The densities of pure methanol were measured for calibration purposes. The volumetric properties in the supercritical region were compared with predictions obtained by a cubic three parameter equations of state. On this base a correlation for the volumetric properties of the reacting mixtures is proposed.