Monday, May 5, 2008
9-13

Liquid-liquid equilibria for castor oil+glycerol+alcohol

Fernando L.P. Pessoa1, Bruno B. França2, Angela M. C. Uller2, and Fabio P. Moraes1. (1) Biochemical Engineering Department, Universidade Federal do Rio de Janeiro, CT, Bl. E, Cidade Universitária, 21949-900, Rio de janeiro, Brazil, (2) Peq-Coppe, Universidade Federal do Rio de Janeiro, CT, Bl. G, Cidade Universitária, Rio de janeiro, Brazil

Biodiesel can be produced through transesterification reaction of vegetable oils or animal fats with alcohol, generally methanol or ethanol, in the presence of a catalyst. Besides the alkyl esters, this reaction forms glycerol along with mono and diglycerides. For most vegetable oils, the products form two liquid phases, one rich in glycerol and the other in biodiesel with alcohol distributed in both phases. The mixture can easily be separated by decantation. When castor oil is used as a feedstock the mutual solubility of the products is high and only one phase is obtained due to the fact that the corresponding esters have a hydroxyl group in their chains causing an increasing in solubility. The objective of the present work is to study the phase equilibrium behavior of the system biodiesel+glycerol+alcohol to provide experimental data for the optimization of the separation down stream processes. The measurements of liquid-liquid equilibrium were carried out for the ternary systems containing biodiesel derived from castor +glycerol+methanol at 25°C and +ethanol at 25 and 60°C. An increase of the system mutual solubility was observed with temperature. The phase boundary was determined by turbidimetric analysis using the titration method under isothermal conditions. The tie lines were indirectly measured by analyzing the mixture density.

 Keywords: biodiesel, ternary systems, methanol, ethanol


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