Optimization of the methylic biodiesel purification process by intermediate of liquid–liquid equilibrium data for ternary systems containing methanol + water + (soybean, corn or brown shell of coconut) biodiesel

• LLE data has been studied in order to optimize biodiesel purification process.
• LLE data were correlated with different activity coefficient models.
• The influence of temperature plays a minor role on the purification process.
• The use of methanol as extractor can accelerate the purification of biodiesel.

Biodiesel is usually produced by transesterification reactions, by intermediate of a catalytic reaction in which a source of triglycerides (from vegetable, animal or residual oils) reacts with excess of alcohol producing as main product biodiesel and as side-product glycerol. After those reactions, it is usually necessary to purify the biodiesel produced by settling process. This step is followed by liquid–liquid extraction (wash up) unit operation. Systematic studies on biodiesel washing process, especially as function of composition data, are still scarce in the literature. Liquid–liquid equilibrium data provide important means to the development and design of equipment and also in the optimization of the extraction processes. This paper, as part of continuing study in our research group, reports equilibrium data for different ternary systems of methanol + water + (soybean, corn or brown shell of coconut, here named coconut) biodiesel at 293.15 and 313.15 K at atmospheric pressure. Experimental data were carried out in equilibrium cells, by using a bath, in order to control the temperature of the system. From experimental data, distribution coefficients of methanol have been determined. The quality and reliability of the tie-line were tested by Othmer-Tobias and Hand correlations. Liquid–liquid equilibrium (LLE) data were correlated with the following activity coefficient models: NRTL, UNIQUAC and UNIFAC, with a global deviation error of 1.34%, 1.34% and 4.13%, respectively.

System of (soybean, corn and coconut) biodiesel + methanol + water. Experimental data at 293.15 K. Soybean biodiesel (■); corn biodiesel (○) and coconut biodiesel (×).Figure optionsDownload as PowerPoint slide