Continuous production of triacetin-blended biodiesel from palm fatty acid distillate using a microreactor under supercritical conditions

This study demonstrates a continuous microreactor process for producing triacetin-blended biodiesel from palm fatty acid distillate (PFAD), a low-cost, high-FFA feedstock, under supercritical methyl acetate conditions, thereby extending this glycerol-free route to low-quality feedstocks. The effects of reaction temperature, residence time, and methyl acetate-to-PFAD molar ratio were systematically investigated and optimized using response surface methodology. The optimum conditions were 390 °C, 40 min, and a methyl acetate-to-PFAD molar ratio of 10.2:1, yielding 89.2% FAME and 3.1 wt% triacetin. The resulting triacetin-blended biodiesel showed a 3.1% reduction in cloud point compared with triacetin-free biodiesel. The effects of co-reactive solvents were also evaluated. The addition of 12 wt% methanol increased the FAME content to 91.6%, whereas the addition of water had no significant positive effect. Compared with supercritical methyl acetate processes using refined palm oil, the developed process achieved competitive biodiesel production performance, with higher productivity (1.20×10⁻³ kg_biodiesel/h, lower solvent intensity (2.99 kg_solvent/kg_biodiesel), and lower process mass intensity (4.11 kg_inputs/kg_biodiesel), indicating improved material efficiency and environmental sustainability. These findings highlight the potential of the proposed process for upgrading low-cost feedstocks into value-added triacetin-blended biodiesel, offering a promising pathway toward more sustainable biodiesel production.