Liquid-liquid equilibrium for ternary system containing biodiesel, methanol and water

Biodiesel is described as a renewable substitute to diesel fuel derived from oil and is currently being used in road transport systems. Nowadays, biodiesel is produced from vegetable oils or animal fats by transesterification using homogenous catalytic processes. This process results in high operatory costs, due to the cost of raw materials used, and also to the need to purify the obtained biodiesel. This paper describes the determination of binodal (Liquid-Liquid equilibria, LLE) curves for the ternary system biodiesel/methanol/water, as a function of temperature. These are basic thermodynamic data required for the efficient design of liquid-liquid extraction units used in the production process. The obtained curves showed the existence of an immiscible system between biodiesel and water. Only for mixtures with less than 4–5% of biodiesel in methanol, some solubilization of biodiesel in water and methanol takes place. This points out that liquid-liquid extraction columns can be quite effective in order to extract methanol from the biodiesel phase, in the washing phases of the continuous purification processes of biodiesel production.