Transformation of Residual Fatty Biomass into Green Diesel: Optimization of the Reaction Parameters over a MoNi/SiO2 Catalyst

Abstract

To advance the circular bioeconomy and mitigate fossil fuel dependency, this study evaluates the catalytic valorization of diverse residual fatty biomasses into high-quality renewable (green) diesel. A high-loading bimetallic MoNi/SiO2 catalyst (metal loading: 50 wt %, atomic ratio: Ni/(Ni + Mo) = 0.95) was developed via wet impregnation for hydrodeoxygenation reactions. Under optimized experimental conditions (350 °C, 40 bar), the catalyst achieved a 100 wt % diesel-range hydrocarbon in the liquid product from waste cooking oil (WCO), chicken fat (CHF), and pork fat (POF). Conversely, fatty acid distillates (FAD) and spent coffee ground oil (SCGO) resulted in lower efficiencies (85 and 78 wt %, respectively). The catalyst demonstrated excellent stability during WCO, CHF, and POF hydrodeoxygenation; a minor efficiency decline after the second run was fully restored via thermal regeneration, identifying coking as the primary cause of temporary deactivation. In contrast, FAD and SCGO processing induced a more pronounced efficiency drop after the second cycle, with only partial performance recovery post-regeneration. This behavior confirms that irreversible deactivation is triggered by nitrogenous compounds, supplemented by moisture-induced effects in SCGO. These insights stress the possibility of exploring hazardous fatty wastes by converting them into drop-in biofuels, directly supporting industrial decarbonization efforts.