Modelling of non-catalytic biodiesel synthesis under sub and supercritical conditions: The influence of phase distribution

Biodiesel, a mixture of fatty acid methyl esters, is widely used as renewable bio-based alternative fuel for internal combustion engines. Kinetic model of non-catalytic biodiesel synthesis at elevated temperature and pressure, based on triglycerides conversion, is presented in this study. The model was developed using experimental reaction data of non-catalytic biodiesel synthesis at 150 and 210 °C, and under pressures of 1.0 and 4.5 MPa, respectively. The phase transition during transesterification at different conditions (subcritical and supercritical) and limitations of mass transfer between two liquid phases were included in the model. This complex reaction was represented by kinetic model with three consecutive and parallel reversible reactions, while kinetic parameters were calculated using simplified procedure based on triglycerides conversion as the only variable. The developed model was found to fit the experimental data for triglyceride conversion with high accuracy.

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► The model of non-catalytic triglycerides alcoholysis at elevated p,T was developed.
► The phase distribution and mass transfer of reacting species were included in the model.
► Simplified procedure for the determination of kinetic constants was proposed.
► The model assumes that all consecutive steps in this complex reaction are reversible.
► The predicted and experimental data were in excellent agreement for a broad range of p,T conditions.