Waste-to-Biofuel Conversion: Hydrodeoxygenation ofFrying Oil over NiMoS2/Al2O3 forthe Production of Renewable Hydrocarbons

Abstract Renewable hydrocarbons were produced from soybean oil (SO) and frying oil (FO) through hydrotreatment over a commercial NiMoS2/Al2O3 catalyst. The effects of temperature (350, 360, and 370 °C), hydrogen pressure (50, 60, and 70 bar), and stirring speed (500, 650, and 800 rpm) were investigated through a 23 factorial design in a batch reactor operated for 5 h with 3 wt % catalyst loading. High catalytic activity was observed for both feedstocks, with XTG (triacylglyceride conversions) above 98% under most experimental conditions. The optimum condition (370 °C, 70 bar, and 800 rpm) resulted in hydrocarbon selectivity (SHC) above 97% and selectivity toward the green diesel range (C16–C22 n-paraffins) (SGD) reached 95.12%. Statistical analysis identified temperature as the most significant influential variable, followed by hydrogen pressure, whereas stirring speed showed no significant effect. The fitted models exhibited high predictive capability (R2 > 0.96). Catalyst reuse tests maintained conversions above 93%, although a gradual loss of activity possibly associated with coke formation was observed. The results demonstrate that commercial NiMoS2/Al2O3 catalysts are effective for converting both refined and residual oils into SGD, highlighting the potential of frying oil as a low-cost feedstock for sustainable fuel production.