In-situ hydrodeoxygenation of anisole as a representative compound of bio-oil oxygenates to biofuel over Ni-Mo/γ-Al2O3 catalyst

In-situ hydrodeoxygenation of anisole, a model compound representing bio-oil oxygenates, was investigated under varying reaction conditions. The influence of catalyst loading, time, temperature, ethanol-to-anisole molar ratio, water-to-ethanol ratio, alcohol type and stability of the catalyst was systematically analyzed. The results revealed that increasing temperature and time enhanced anisole conversion to about 62.78 % and 100 % but also led to a shift in selectivity, reducing cyclohexane formation while promoting alternative reaction pathways. Higher catalyst loadings improved conversion to 100 %, though excessive loading altered product selectivity. The ethanol-to-anisole molar ratio demonstrated a critical impact, with intermediate ratios yielding the highest conversion (54.08 %), whereas excessive ethanol concentrations hindered the reaction to a conversion of 21.98 %. Similarly, the water-to-ethanol molar ratio influenced conversion (61.06 %), with moderate water content enhancing efficiency while affecting selectivity patterns. The choice of alcohol significantly dictated reaction outcomes, where methanol and isopropyl alcohol led to higher conversions (94.41 %) compared to ethanol, while methanol favored cyclohexane formation, and isopropyl alcohol promoted methoxycyclohexane production. By fine-tuning these variables, selectivity toward desirable hydrocarbon products can be maximized while minimizing the formation of unwanted by-products. Under optimized conditions (300 °C, 6 h reaction time, 10 wt% catalyst loading, ethanol-to-anisole molar ratio of 10, and water-to-ethanol ratio of 3), nearly complete anisole conversion (∼100 %) was achieved with cyclohexane selectivity of ∼90 %. These findings demonstrate the potential of in-situ HDO over Ni-Mo/γ-Al2O3 for efficient upgrading of lignin-derived bio-oil model compounds into desirable hydrocarbon fuels.