Liquid–Liquid Equilibrium in Biodiesel Production Systems
Summary
Liquid–liquid equilibrium (LLE) plays a critical role in the separation, purification and yield optimisation of biodiesel production systems. During transesterification of triglyceride feedstocks with short-chain alcohols, a biphasic liquid mixture emerges, comprising fatty acid methyl or ethyl esters (biodiesel) and a glycerol-rich phase. Knowledge of phase behaviour informs reactor design, extraction processes and continuous operation strategies by specifying conditions under which the two product phases disengage effectively. Variation in temperature, feed composition and choice of co-solvents or catalysts significantly alters binodal boundaries and tie-line distributions, thereby influencing separation efficiency, purity of the final biodiesel and recycling of unreacted alcohol. Thermodynamic models, such as the non-random two-liquid (NRTL) and UNIQUAC equations, are routinely fitted to experimental data to predict phase compositions, guide scale-up and minimise energy input. Advances in LLE research have global significance, supporting sustainable production routes from waste oils and novel feedstocks while reducing downstream processing costs and environmental impact.
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Liquid–Liquid Equilibrium in Biodiesel Production Systems publication trend
The graph below shows the total number of articles in liquid–liquid equilibrium in biodiesel production systems across all publications each year (not limited to Nature Index journals).
Technical terms
Liquid–Liquid Equilibrium: Coexistence of two immiscible liquid phases with distinct compositions under equilibrium conditions.
Binodal curve: Boundary in composition space marking the onset of phase separation.
Tie line: Line connecting the equilibrium compositions of coexisting phases at a given temperature.
Transesterification: Chemical reaction in which triglycerides react with alcohol to form esters (biodiesel) and glycerol.
Activity coefficient: Factor quantifying the deviation of a component’s behaviour from that in an ideal solution.
NRTL model: Thermodynamic framework (non-random two-liquid) used to calculate activity coefficients and predict phase equilibria.
References
- Liquid–Liquid Equilibrium of Sesame Fatty Acid (Ethyl and Methyl) Ester + Glycerol + Ethanol/Methanol Mixtures at Different Temperatures. Molecules (2024).
- LIQUID-LIQUID EQUILIBRIUM OF SYSTEMS COMPOSED OF SOYBEAN OIL + MONOACYLGLYCEROLS + DIACYLGLYCEROLS + ETHYL OLEATE + OLEIC ACID + ETHANOL AT 303.15 AND 318.15 K. Brazilian Journal of Chemical Engineering (2018).
- Liquid–Liquid Equilibrium Behavior of Ternary Systems Comprising Biodiesel + Glycerol and Triglyceride + Methanol: Experimental Data and Modeling. Catalysts (2024).
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