Microalgae-based sustainable aviation fuel: Kinetic framework, process simulation, and fuel property analysis

Microalgae-derived lipids are a high-productivity feedstock for sustainable aviation fuel (SAF) via the hydroprocessed esters and fatty acids (HEFA) pathway. However, previous simulations often oversimplify hydroisomerisation kinetics by restricting reaction networks to single components or truncated cracking ranges, inherently distorting predicted hydrocarbon distributions and compromising critical cold-flow property estimations. To address this knowledge gap, this study develops an extended kinetic framework for the isomerisation and deep hydrocracking of C15–C18 alkanes down to four-carbon (C4) products, integrating a unified kinetic treatment for long-chain homologues. Validated against experimental data, the proposed model achieves a mean absolute error (MAE) of 4.24%, outperforming alternatives with C8-limited cracking (MAE = 4.86%) or C16-only isomerisation (MAE = 15.67%). Crucially, Aspen Plus simulations reveal that simplified networks generate severe compositional artefacts: C16-only isomerisation models leave dominant heavy fractions un-isomerised (overestimating the freezing point to −5.24°C), while C8-limited cracking models artificially eliminate C11–C14 intermediate hydrocarbons (underestimating the freezing point to −47.46°C). The extended model effectively eliminates these distortions, yielding a realistic product distribution with a sound freezing point (−39.19°C) and density (736.23 kg/m3). Ultimately, these findings highlight the necessity of rigorous kinetic modelling to mitigate design risks and ensure reliable property predictions for SAF biorefinery scale-up.