(508c) Simulation of the Absorption of Gasoline Volatile Organic Compounds in Biodiesel

The fatty acid methyl esters (FAME) obtained by transesterification of vegetable oil and better known as biodiesel is a mixture with high boiling point, low toxicity, low volatility and a high dissolving power in organic compounds. These characteristics make of biodiesel a suitable solvent in absorption processes such as the recovery of volatile organic compounds (VOC's). The problem addressed in this work is the release of C₄ to C₇ alkanes that occurs when high volume auto tanks are being filling up with gasoline. Besides preventing atmospheric pollution, the absorption of C₅⁺ volatile compounds is economically very important since a high amount of gasoline can be recovered. Thus, this work studies the thermodynamic feasibility of using biodiesel as an efficient absorber of gasoline VOC's. A detailed liquid-vapor equilibrium investigation was carried out at different temperatures by using group contribution methods mainly UNIFAC and a commercial simulator (ASPEN PLUS). The interaction of biodiesel and VOC's was estimated by their Henry's law constants and infinite dilution activity coefficients. The simulation was applied to an industrial absorption plant that currently uses a non-renewable and non-enviromentally friendly solvent. The simulation data showed the feasibility of using biodiesel as an efficient absorbent of VOC's, as well as the feasibility of recovering it after being used.