Thermally induced transesterification of Prunus mume seed into biodiesel using dimethyl carbonate as a green acyl acceptor

Abstract

Anthropogenic climate change, driven by extensive fossil fuel combustion, needs a transition toward carbon–neutral transportation systems. Among renewable fuel candidates, biodiesel is notable for its physico-chemical compatibility with petroleum-derived diesel; however, its large-scale deployment is constrained by sustainability concerns, including dependence on edible lipid feedstocks and the high energy demand associated with lipid extraction. This study introduces a non-catalytic conversion platform for the direct transesterification of fruit seeds into biodiesel, eliminating the need for prior lipid extraction. Prunus mume seed, containing 30–45 wt% lipids, was selected as the model feedstock. To enhance process sustainability, dimethyl carbonate was used as an acyl acceptor in place of methanol, owing to its low toxicity and environmentally benign characteristics. Benchmark experiments involved acid-, base-, and non-catalytic transesterification of Prunus mume oil with methanol. The base-catalyzed method using methanol achieved a maximum biodiesel yield of 80.29 wt% at 63 ˚C within 60 min. In contrast, non-catalytic methanol-based conversion at 350 ˚C produced 90.02 wt% biodiesel in 1 min, despite the presence of high levels of free fatty acids and non-lipid impurities, demonstrating high impurity tolerance and rapid reaction kinetics. Under identical non-catalytic conditions, dimethyl carbonate achieved a higher yield of 95.26 wt%, likely attributable to improved mass transfer to hydrophobic triglycerides and free fatty acids resulting from its lower polarity. Direct seed conversion without lipid extraction yielded 42.9 wt% biodiesel at 360 ˚C within 1 min, exceeding the lipid content determined by solvent extraction (33.9 wt%) by 1.2-fold and indicating incomplete lipid recovery.